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Atoms: The Building Blocks of Matter. Foundations of Atomic Theory. Nearly all chemists in late 1700s accepted the definition of an element as a substance that cannot be broken down further Knew about chemical reactions

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Foundations of atomic theory
Foundations of Atomic Theory

  • Nearly all chemists in late 1700s accepted the definition of an element as a substance that cannot be broken down further

  • Knew about chemical reactions

  • Great disagreement as to whether elements always combine in the same ratio when forming a specific compound


Law of conservation of mass
Law of Conservation of Mass

  • With the help of improved balances, investigators could accurately measure the masses of the elements and compounds they were studying

  • This lead to discovery of several basic laws

  • Law of conservation of mass states that mass is neither destroyed nor created during ordinary chemical reactions or physical changes


Law of definite proportions
Law of Definite Proportions

  • law of definite proportions  A chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound

Each of the salt crystals shown here contains exactly

39.34% sodium and 60.66% chlorine by mass.


Law of multiple proportions
Law of Multiple Proportions

  • Two elements sometimes combine to form more than one compound

    • For example, the elements carbon and oxygen form two compounds, carbon dioxide and carbon monoxide

  • Consider samples of each of these compounds, each containing 1.0 g of carbon


Atoms the building blocks of matter



1808 john dalton
1808 John Dalton exactly 2.66 to 1.33, or 2 to 1

  • Proposed an explanation for the law of conservation of mass, the law of definite proportions, and the law of multiple proportions


Atoms the building blocks of matter


Atoms the building blocks of matter


Dalton s atomic theory
Dalton’s Atomic Theory only whole numbers of atoms can combine to form compounds

  • All matter is composed of extremely small particles called atoms.

  • Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.

  • Atoms cannot be divided, created or destroyed.

  • Atoms of different elements combine in simple whole-number ratios to form chemical compounds.

  • In chemical reactions, atoms are combined, separated, or rearranged.


Modern atomic theory
Modern Atomic Theory only whole numbers of atoms can combine to form compounds

  • Dalton turned Democritus’sidea into a scientific theory which was testable

  • Not all parts of his theory have been proven correct


Atoms the building blocks of matter


Structure of the atom
Structure of the Atom only whole numbers of atoms can combine to form compounds


All atoms consist of two regions
All atoms consist of two regions only whole numbers of atoms can combine to form compounds

  • Nucleus very small region located near the center of an atom

    • In the nucleus there is at least one positively charged particle called the proton

    • Usually at least one neutral particle called the neutron

  • Surrounding the nucleus is a region occupied by negatively charged particles called electrons


Discovery of the electron
Discovery of the Electron only whole numbers of atoms can combine to form compounds

  • Resulted from investigations into the relationship between electricity and matter

  • Late 1800s, many experiments were performed  electric current was passed through different gases at low pressures


Atoms the building blocks of matter


Cathode rays and electrons
Cathode Rays and Electrons only whole numbers of atoms can combine to form compounds

  • Investigators noticed that when current was passed through a cathode-ray tube, the opposite end of the tube glowed


Atoms the building blocks of matter


Observations
Observations particles, which they called a cathode ray

  • 1. cathode rays deflected by magnetic field in same way as wire carrying electric current (known to have negative charge)

  • 2. rays deflected away from negatively charged object


Atoms the building blocks of matter


Atoms the building blocks of matter


Atoms the building blocks of matter


Charge and mass of the electron
Charge and Mass of the Electron identical negatively charged particles, which were later named

  • Confirmed that the electron carries a negative electric charge

  • Because cathode rays have identical properties regardless of the element used to produce them, it was concluded that electrons are present in atoms of all elements


Atoms the building blocks of matter


Atoms the building blocks of matter

  • Thomson’s experiment revealed that the electron has a very large charge for its tiny mass

  • Mass of the electron is about one two-thousandth the mass of the simplest type of hydrogen atom (the smallest atom known)

  • Since then found that the electron has a mass of 9.109 × 10−31 kg, or 1/1837 the mass of the hydrogen atom


Atoms the building blocks of matter


Thomson s atom
Thomson’s Atom about atomic structure

  • Plum pudding model (based on English dessert)

  • Negative electrons spread evenly through positive charge of the rest of the atom

  • Like seeds in a watermelon


Discovery of atomic nucleus
Discovery of Atomic Nucleus about atomic structure

  • 1911 by New Zealander Ernest Rutherford and his associates Hans Geiger and Ernest Marsden

  • Bombarded a thin, gold foil with fast-moving alpha particles (positively charged particles with about four times the mass of a hydrogen atom)


Atoms the building blocks of matter


What really happened
What atoms of gold foil (from Thomson’s model of the atom)Really Happened…

  • Most particles passed with only slight deflection

  • However, 1/8,000 were found to have a wide deflection


Atoms the building blocks of matter


Explanation
Explanation 15-inch artillery shell at a piece of tissue paper and it came back and hit you.”

  • After 2 years, Rutherford finally came up with an explanation

  • The rebounded alpha particles must have experienced some powerful force within the atom


Atoms the building blocks of matter


Atoms the building blocks of matter


Atoms the building blocks of matter


Atoms the building blocks of matter


Rutherford s atom
Rutherford’s Atom positively charged nucleus like planets around the sun


Composition of atomic nucleus
Composition of Atomic Nucleus positively charged nucleus like planets around the sun

  • Except hydrogen, all atomic nuclei made of two kinds of particles

    • Protons

    • Neutrons


Atoms the building blocks of matter

  • Protons = positive positively charged nucleus like planets around the sun

  • Neutrons = neutral

  • Electrons = negative



Atoms the building blocks of matter


Forces in the nucleus
Forces in the Nucleus number of protons they contain and therefore in the amount of positive charge they possess

  • Usually, particles that have the same electric charge repel one another

  • Would expect a nucleus with more than one proton to be unstable



Atoms the building blocks of matter

  • Nuclear forces a strong attraction between them short-range proton-neutron, proton-proton, and neutron-neutron forces that hold the nuclear particles together


The sizes of atoms
The Sizes of atoms a strong attraction between them

  • Area occupied by electrons is electron cloud – cloud of negative charge

  • Radius of atom is distance from center of nucleus to outer portion of cloud


Atoms the building blocks of matter

  • Unit – a strong attraction between thempicometer (10-12 m)

  • Atomic radii range from 40-270 pm

  • Very high densities – 2 x 108 tons/cm3


Counting atoms
Counting Atoms a strong attraction between them


Atomic number
Atomic Number a strong attraction between them

  • Atoms of different elements have different numbers of protons

  • Atomic number (Z) number of protons in the nucleus of each atom of that element

  • Shown on periodic table

  • Atomic number identifies an element

3

Li

Lithium

6.941

[He]2s1


Isotopes
Isotopes a strong attraction between them

  • Hydrogen and other atoms can contain different numbers of neutrons


Atoms the building blocks of matter

  • Isotope a strong attraction between them atoms of same element that have different masses


Isotopes of hydrogen
Isotopes of Hydrogen a strong attraction between them


Mass number
Mass Number a strong attraction between them

  • Mass number total number of protons and neutrons in the nucleus of an isotope


Sample problem
Sample Problem a strong attraction between them

  • How many protons, electrons, and neutrons are there in an atom of chlorine-37?


Atoms the building blocks of matter


Atoms the building blocks of matter


Practice problems
Practice Problems number of neutrons in chlorine-37

  • How many protons, electrons, and neutrons are in an atom of bromine-80?

  • Answer 35 protons, 35 electrons, 45 neutrons


Atoms the building blocks of matter

2. Write the nuclear symbol for carbon-13. number of neutrons in chlorine-37

  • Answer 136C


Atoms the building blocks of matter

3. Write the hyphen notation for the element that contains 15 electrons and 15 neutrons.

  • Answer phosphorus-30


Relative atomic masses
Relative Atomic Masses 15 electrons and 15 neutrons.

  • Because atoms are so small, scientists use a standard to control the units of atomic mass  carbon-12

  • Randomly assigned a mass of exactly 12 atomic mass units (amu)


Atoms the building blocks of matter

  • 1 15 electrons and 15 neutrons.amu is exactly 1/12 the mass of a carbon-12 atom

  • Atomic mass of any atom determined by comparing it with mass of C-12

  • Ex. H  1/12 C-12, so 1 amu


Average atomic masses
Average Atomic Masses 15 electrons and 15 neutrons.

  • Average atomic mass the weighted average of the atomic masses of the naturally occurring isotopes of an element


Atoms the building blocks of matter


Calculating average atomic mass
Calculating Average Atomic Mass 15 electrons and 15 neutrons.

Copper

69.17% Cu-63 – 62.929599 amu

30.83% Cu-65 – 64.927793 amu

(0.6917 x 62.929599) + (0.3083 x 64.927793)

= 63.55 amu


Relating mass to numbers of atoms
Relating Mass to Numbers of Atoms 15 electrons and 15 neutrons.

  • The relative atomic mass scale makes it possible to know how many atoms of an element are present in a sample of the element with a measurable mass


Atoms the building blocks of matter


The mole
The Mole masses in grams to numbers of atoms

  • SI unit for an amount of substance (like 1 dozen = 12)

  • Mole (mol)  amount of a substance that contains as many particles as there are atoms in exactly 12g of C-12


Avogadro s number
Avogadro’s Number masses in grams to numbers of atoms

  • Avogadro’s number the number of particles in exactly one mole of a pure substance

  • 6.022 x 1023

  • How big is that?


Atoms the building blocks of matter


Molar mass
Molar Mass an element, and if each person counted continuously at a rate of one atom per second, it would take about 4 million years for all the atoms to be counted

  • Molar mass the mass of one mole of a pure substance

  • Written in unit g/mol


Atoms the building blocks of matter

  • Found on periodic table (atomic mass) an element, and if each person counted continuously at a rate of one atom per second, it would take about 4 million years for all the atoms to be counted

  • Ex. Molar mass of H = 1.008 g/mol


Example
Example an element, and if each person counted continuously at a rate of one atom per second, it would take about 4 million years for all the atoms to be counted

How many grams of helium are there in 2 moles of helium?

2.00 mol He x = ? g He

2.00 mol He x 4.00 g He = 8.00 g He

1 mole He


Practice problems1
Practice Problems an element, and if each person counted continuously at a rate of one atom per second, it would take about 4 million years for all the atoms to be counted

What is the mass in grams of 3.50 mol of the element copper, Cu?

222 g Cu

What is the mass in grams of 2.25 mol of the element iron, Fe?

126 g Fe


Atoms the building blocks of matter

What is the mass in grams of 0.375 an element, and if each person counted continuously at a rate of one atom per second, it would take about 4 million years for all the atoms to be countedmol of the element potassium, K?

14.7 g K

What is the mass in grams of 0.0135 mol of the element sodium, Na?

0.310 g Na


Atoms the building blocks of matter

What is the mass in grams of 16.3 an element, and if each person counted continuously at a rate of one atom per second, it would take about 4 million years for all the atoms to be countedmol of the element nickel, Ni?

957 g Ni



Atoms the building blocks of matter

How aluminum were produced?many moles of calcium, Ca, are in 5.00 g of calcium?

0.125 mol Ca


Atoms the building blocks of matter

How aluminum were produced?many moles of gold,Au, are in 3.60 × 10−10 g of gold?

1.83 × 10−12 mol Au


Conversions with avogadro s number
Conversions with Avogadro’s Number aluminum were produced?

How many moles of silver, Ag, are in 3.01 x 1023 atoms of silver?

Given: 3.01 × 1023 atoms of Ag

Unknown: amount of Ag in moles

Ag atoms × = moles Ag

3.01x1023atomsAg x =0.500 mol Ag


Practice problems2
Practice problems aluminum were produced?

How many moles of lead, Pb, are in 1.50 × 1012 atoms of lead?

2.49 × 10−12 mol Pb


Atoms the building blocks of matter

How aluminum were produced?many moles of tin, Sn, are in 2500 atoms of tin?

4.2 × 10−21 mol Sn


Atoms the building blocks of matter

How aluminum were produced?many atoms of aluminum, Al, are in 2.75 mol of aluminum?

1.66 × 1024 atoms Al


Atoms the building blocks of matter

What is the mass in grams of 7.5 × 10 aluminum were produced?15 atoms of nickel, Ni?

7.3 × 10−7 g Ni


Atoms the building blocks of matter

How aluminum were produced?many atoms of sulfur, S, are in 4.00 g of sulfur?

7.51 × 1022 atoms S


Atoms the building blocks of matter

What aluminum were produced?mass of gold,Au, contains the same number of atoms as 9.0 g of aluminum,Al?

66 g Au


Arrangement of electrons in atoms

Arrangement of Electrons in Atoms aluminum were produced?


Atoms the building blocks of matter

  • Visible light is a kind of aluminum were produced?electromagnetic radiation form of energy that exhibits wavelike behavior as it travels through space

    • X-rays, UV, infrared, etc.

  • Together, all forms of electromagnetic radiation form the electromagnetic spectrum


Properties of em radiation
Properties of EM Radiation aluminum were produced?

  • All forms of EM radiation travel at a constant speed (3.0 × 108 m/s) through a vacuum and at slightly slower speeds through matter


Atoms the building blocks of matter


Atoms the building blocks of matter

  • Wavelength (λ) measurable properties  the distance between corresponding points on neighboring waves

  • Frequency (ν)  the number of waves that pass a given point in a specific time, usually one second


The photoelectric effect
The Photoelectric Effect measurable properties

  • Early 1900s, scientists conducted two experiments involving relations of light and matter that could not be explained by the wave theory of light


Atoms the building blocks of matter


The mystery
The Mystery photoelectric effect

  • For a given metal, no electrons were emitted if the light’s frequency was below a certain minimum—regardless of how long the light was shone

  • Light was known to be a form of energy, capable of knocking loose an electron from a metal


Atoms the building blocks of matter


The particle description of light
The Particle Description of Light supply enough energy to eject an electron

  • Explanation  1900, German physicist Max Planck was studying the emission of light by hot objects

  • Proposed a hot object does not emit electromagnetic energy continuously, as would be expected if the energy emitted were in the form of waves


Atoms the building blocks of matter


Atoms the building blocks of matter

  • Planck projected the following relationship between a quantum of energy and the frequency of radiation

    E = hν

  • In the equation,

    • E is the energy, in joules, of a quantum of radiation

    • ν is the frequency of the radiation emitted

    • h is a constant now known as Planck’s constant

      • h = 6.626 × 10−34 J• s


1905 albert einstein
1905 Albert Einstein quantum of energy and the frequency of radiation

  • Expanded on Planck’s theory by introducing the idea that electromagnetic radiation has a dual wave-particle nature

  • Light displays many wavelike properties, it can also be thought of as a stream of particles


Atoms the building blocks of matter



The hydrogen atom line emission spectrum
The Hydrogen-Atom Line-Emission Spectrum the radiation

  • When current is passed through a gas at low pressure, the potential energy of some of the gas atoms increases


Atoms the building blocks of matter


Returning to ground state
Returning to Ground State the radiation

  • When an excited atom returns to its ground state, it gives off the energy it gained in the form of electromagnetic radiation

  • Example of this process is a neon sign

Excited neon atoms emit light when falling back to the ground state or to a lower-energy excited state.


Atoms the building blocks of matter


Atoms the building blocks of matter


Atoms the building blocks of matter


Bohr model of the hydrogen atom
Bohr Model of the Hydrogen Atom to another) is done in isolated quanta

  • Solved in 1913 by the Danish physicist Niels Bohr

  • Proposed a model of the hydrogen atom that linked the atom’s electron with photon emission



Atoms the building blocks of matter


Atoms the building blocks of matter


The rungs of a ladder
The Rungs of a Ladder space where the electron cannot exist

  • The electron orbits or atomic energy levels in Bohr’s model can be compared to the rungs of a ladder

  • When you are standing on a ladder, your feet are on one rung or another


Atoms the building blocks of matter



Moving up in the orbit
Moving up in the Orbit… but not in between

  • Explaining spectral lines:

  • While in a given orbit, electron isn’t gaining or losing energy


Atoms the building blocks of matter


Atoms the building blocks of matter


Atoms the building blocks of matter


Atoms the building blocks of matter


Atoms the building blocks of matter


Electrons as waves
Electrons as Waves to the energy difference between the initial higher-energy orbit and the final lower-energy orbit

  • Photoelectric effect and H spectrum showed light behaving as wave and particle


Atoms the building blocks of matter


Atoms the building blocks of matter

  • DeBroglie to the energy difference between the initial higher-energy orbit and the final lower-energy orbit pointed out behavior of electrons in Bohr’s orbits similar to known behavior of waves


Atoms the building blocks of matter


Atoms the building blocks of matter


The heisenberg uncertainty principle
The Heisenberg Uncertainty Principle to the energy difference between the initial higher-energy orbit and the final lower-energy orbit

  • If electrons are both particles and waves, then where are they in the atom?

  • To answer this question, it is important to consider a proposal first made in 1927 by the German theoretical physicist Werner Heisenberg


Atoms the building blocks of matter


Atoms the building blocks of matter


Schrodinger wave equation
Schrodinger Wave Equation interaction with photons

  • Used hypothesis that electrons have dual nature to develop equation that treated electrons in atoms as waves

  • Bohr assumed quantization was fact

  • Schrodinger didn’t assume – it was a natural result of his equation


Atoms the building blocks of matter


Atoms the building blocks of matter

  • Quantum theory solutions to equation – describes mathematically the wave properties of electrons and other small particles


Orbitals
Orbitals solutions to equation

  • Electrons do not travel around the nucleus in neat orbits

  • Instead, they exist in certain regions called orbitals


Atoms the building blocks of matter

  • Orbital solutions to equation a three-dimensional region around the nucleus that indicates the probable location of an electron


Atomic orbitals and quantum numbers
Atomic Orbitals and Quantum Numbers solutions to equation

  • Bohr’s model – electrons of increasing energy occupy orbits farther and farther from nucleus


Atoms the building blocks of matter


Atomic orbitals and quantum numbers1
Atomic quantized energiesOrbitals and Quantum Numbers

  • In order to completely describe orbitals, scientists use quantum numbers

  • Quantum numbers  specify the properties of atomic orbitals and theproperties of electrons in orbitals


Atoms the building blocks of matter


The quantum numbers
The Quantum Numbers equation

  • Principal quantum number  the main energy level occupied by the electron

  • Angular momentum quantum number  the shape of the orbital

  • Magnetic quantum number  the orientation of the orbital around the nucleus

  • Spin quantum number  the two fundamental spin states of an electron in an orbital


Principal quantum number
Principal Quantum Number equation

  • Symbolized by n

  • Indicates the main energy level occupied by the electron

  • Values are positive integers only

  • As n increases, the electron’s energy and its average distance from the nucleus increase


Angular momentum quantum number
Angular Momentum Quantum Number equation

  • Except at the first main energy level, orbitals of different shapes— known as sublevels—exist for a given value of n

  • The angular momentum quantum number, symbolized by l, indicates the shape of the orbital


Atoms the building blocks of matter

  • The values of equationl allowed are zero and all positive integers less than or equal to n − 1

    • n = 2 can have one of two shapes

    • l = 0 and l = 1


Atoms the building blocks of matter
n equation = 1

  • l = 0 only

  • For l = 0, the corresponding letter designation for the orbital shape is s

  • Shape of s is a sphere


Atoms the building blocks of matter
n equation = 2

  • l = 0 (s), l = 1 (p)

  • For l = 1, , the corresponding letter designation for the orbital shape is p

  • Shape of p is


Atoms the building blocks of matter
n equation = 3

  • l = 0 (s), l = 1 (p), l = 2 (d)

  • For l = 2, the corresponding letter designation for the orbital shape is d

  • Shape of d is


Atoms the building blocks of matter
n equation= 4

  • l = 0 (s),1 (p), 2 (d), 3 (f)

  • For l = 3, the corresponding letter designation for the orbital shape is f

  • Shape is too complicated to picture


Atoms the building blocks of matter


Magnetic quantum number
Magnetic Quantum Number number followed by the letter of the sublevel

  • Atomic orbitals can have the same shape but different orientations around the nucleus

  • The magnetic quantum number, symbolized by m, indicates the orientation of an orbital around the nucleus


S orbital
S orbital number followed by the letter of the sublevel

  • Because an s orbital is spherical and is centered around the nucleus, it has only one possible orientation

  • This orientation corresponds to a magnetic quantum number of m = 0

  • There is therefore only one s orbital in each s sublevel


P orbital
P orbital number followed by the letter of the sublevel

  • p orbital can extend along the x, y, or z axis

  • There are therefore three porbitals in each p sublevel, which are designated as px, py, and pzorbitals

  • The three porbitals occupy different regions of space and correspond, in no particular order, to values of m = −1, m = 0, and m = +1


D orbital
D orbital number followed by the letter of the sublevel

  • There are five different d orbitals in each d sublevel

  • The five different orientations, including one with a different shape, correspond to values of m = −2, m = −1, m = 0, m = +1, and m = +2


Spin quantum number
Spin Quantum Number number followed by the letter of the sublevel

  • An electron in an orbital can be thought of as spinning on an axis

  • It spins in one of two possible directions, or states

  • The spin quantum number has only two possible values — +1/2 , −1/2


Atoms the building blocks of matter



Atoms the building blocks of matter

  • Quantum model of atom better than Bohr model b/c it describes the arrangements of electrons in atoms other than hydrogen

  • Electron configuration the arrangement of electrons in an atom

  • b/c atoms of different elements have different numbers of e-, the e- configuration for each element is unique


Atoms the building blocks of matter


Rules governing electron configurations
Rules Governing Electron Configurations possible energies

  • To build up electron configurations for the ground state of any particular atom, first the energy levels of the orbitals are determined


Atoms the building blocks of matter


Aufbau principle
Aufbau according to three basic Principle

  • The first rule shows the order in which electrons occupy orbitals

  • According to the Aufbau principle, an electron occupies the lowest-energy orbital that can receive it


Atoms the building blocks of matter


Atoms the building blocks of matter


Atoms the building blocks of matter


Pauli exclusion principle
Pauli Exclusion Principle orbitals

  • The second rule reflects the importance of the spin quantum number

  • According to the Pauli exclusion principle, no two electrons in the same atom can have the same set of four quantum numbers


Hund s rule
Hund’s orbitals Rule

  • The third rule requires placing as many unpaired electrons as possible in separate orbitals in the same sublevel

  • Electron-electron repulsion is minimized  the electron arrangements have the lowest energy possible


Atoms the building blocks of matter

  • Hund’s orbitals rule orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron, and all electrons in singly occupied orbitals must have the same spin



Electron configuration notation
Electron-Configuration Notation orbitals

  • Electron-configuration notation eliminates the lines and arrows of orbital notation

  • Instead, the number of electrons in a sublevel is shown by adding a superscript to the sublevel designation


Atoms the building blocks of matter


Atoms the building blocks of matter


Sample problem1
Sample Problem orbitals

The electron configuration of boron is 1s22s22p1. How many electrons are present in an atom of boron? What is the atomic number for boron? Write the orbital notation for boron.


Practice problems3
Practice Problems orbitals

  • The electron configuration of nitrogen is 1s22s22p3. How many electrons are present in a nitrogen atom? What is the atomic number of nitrogen? Write the orbital notation for nitrogen.


Practice problems4
Practice Problems orbitals

The electron configuration of fluorine is 1s22s22p5. What is the atomic number of fluorine? How many of its p orbitals are filled? How many unpaired electrons does a fluorine atom contain?

  • Answer

  • 9

  • 2

  • 1


Elements of the second period
Elements of the Second Period orbitals

  • According to Aufbau principle, after 1s orbital is filled, the next electron occupies the s sublevel in the second main energy level

  • Lithium, Li, has a configuration of 1s22s1

  • The electron occupying the 2s level of a lithium atom is in the atom’s highest, or outermost, occupied level


Atoms the building blocks of matter

  • The orbitalshighest occupied level  the electron-containing main energy level with the highest principal quantum number

  • The two electrons in the 1s sublevel of lithium are no longer in the outermost main energy level

  • They have become inner-shell electronselectrons that are not in the highest occupied energy level


Atoms the building blocks of matter


Atoms the building blocks of matter


Elements of third period
Elements of Third Period in an atom of boron,

  • After the outer octet is filled in neon, the next electron enters the s sublevel in the n = 3 main energy level


Atoms the building blocks of matter


Noble gas notation
Noble-Gas Notation in an atom of boron,

  • The Group 18 elements (helium, neon, argon, krypton, xenon, and radon) are called the noble gases


Atoms the building blocks of matter

  • To simplify sodium’s notation, the symbol for neon, enclosed in square brackets, is used to represent the complete neon configuration:

    [Ne] = 1s22s22p6

  • This allows us to write sodium’s electron configuration as [Ne]3s1, which is called sodium’s noble-gas notation


Elements of the fourth period
Elements of the Fourth Period enclosed in square brackets, is used to represent the complete neon configuration:

  • Period begins by filling 4s orbital (empty orbital of lowest energy)

  • First element in fourth period is potassium, K

  • E- configuration [Ar]4s1

  • Next element is calcium, Ca

  • E- configuration [Ar]4s2


Atoms the building blocks of matter


Atoms the building blocks of matter


Atoms the building blocks of matter

  • Scandium has e- configuration [ available empty Ar]3d14s2

  • Titanium, Ti, has configuration [Ar]3d24s2

  • Vanadium, V, has configuration [Ar]3d34s2

  • Up to this point, 3 e- with same spin added to 3 separate d orbitals (required by Hund’s rule)


Atoms the building blocks of matter

  • Chromium, Cr, has configuration [ available empty Ar]3d54s1

  • We added one electron to 4th 3d orbital

  • We also took a 4s electron and added it to 5th 3d orbital

  • Seems to be against Aufbau principle

  • In reality, [Ar]3d54s1 is lower energy than [Ar]3d44s2


Atoms the building blocks of matter

  • Having 6 outer available empty orbitals with unpaired electrons in 3d orbital is more stable than having 4 unpaired electrons in 3d orbitals and forcing 2 electrons to pair in 4s

  • For tungsten, W, (same group as chromium) having 4 e- in 5d orbitals and 2 e- paired in 6s is most stable arrangement

  • No easy explanantion


Atoms the building blocks of matter

  • Manganese, available empty Mn, has configuration [Ar]3d54s2

  • Added e- goes to 4s orbital, completely filling it and leaving 3d half-filled

  • Starting with next element, e- continue to pair in d orbitals


Atoms the building blocks of matter


Atoms the building blocks of matter


Elements of fifth period
Elements of Fifth Period in 5

  • In 18 elements of 5th period, sublevels fill in similar way to 4th period elements

  • BUT they start at 5s level instead of 4s level

  • Fill 5s, then 4d, and finally 5p

  • There are exceptions just like in 4th period


Practice problem
Practice Problem in 5

Write both the complete electron-configuration notation and the noble-gas notation for iron, Fe.


Atoms the building blocks of matter

Write both the complete electron configuration notation and the noble-gas notation for iodine, I. How many inner-shell electrons does an iodine atom contain?

  • 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p65s2 4d10 5p5

  • [Kr]4d10 5s2 5p5

  • 46


Atoms the building blocks of matter

How many electron-containing the noble-gas notation for iodine, I. How many inner-shell electrons does an iodine atom contain?orbitals are in an atom of iodine? How many of these orbitals are filled? How many unpaired electrons are there in an atom of iodine?

  • 27

  • 26

  • 1


Atoms the building blocks of matter

Write the noble-gas notation for tin, the noble-gas notation for iodine, I. How many inner-shell electrons does an iodine atom contain?Sn. How many unpaired electrons are there in an atom of tin?

  • [Kr] 5s2 4d10 5p2

  • 2


Atoms the building blocks of matter

Without consulting the periodic table or a table in this chapter, write the complete electron configuration for the element with atomic number 25.

  • 1s2 2s2 2p6 3s2 3p6 4s2 3d5


Elements of 6 th and 7 th periods
Elements of 6 chapter, write the complete electron configuration for the element with atomic number 25.th and 7th periods

  • 6th period has 32 elements

  • To build up e- configurations for elements in this period, e- first added first to 6s orbital in cesium, Cs, and barium, Ba


Atoms the building blocks of matter


Atoms the building blocks of matter

  • With next element, cerium, chapter, write the complete electron configuration for the element with atomic number 25.Ce, 4f orbitals begin to fill

  • Ce: [Xe]4f15d16s2

  • In next 13 elements, 4f orbitals filled


Atoms the building blocks of matter

  • Next 5d orbitals filled chapter, write the complete electron configuration for the element with atomic number 25.

  • Period finished by filling 6p orbitals

  • (some exceptions happen)


Practice problem1
Practice Problem chapter, write the complete electron configuration for the element with atomic number 25.

Write both the complete electron-configuration notation and the noble-gas notation for a rubidium atom.

  • 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1

  • [Kr]5s1


Atoms the building blocks of matter

Write both the complete electron configuration notation and the noble-gas notation for a barium atom.

  • 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2

  • [Xe]6s2