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ATOMIC STRUCTURE AND ELECTRON CONFIGURATION. CHAPTER THREE . PAGE 73 LET’S READ SOMETHING TO THINK ABOUT!!!! EXCITED ATOMS AND THE FOURTH OF JULY !!!!!. Dalton's Atomic Theory 1) All matter is made of atoms. Atoms are indivisible and indestructible.

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ATOMIC STRUCTURE AND ELECTRON CONFIGURATION

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Atomic structure and electron configuration

ATOMIC STRUCTURE AND ELECTRON CONFIGURATION

CHAPTER THREE


Atomic structure and electron configuration

PAGE 73

LET’S READ SOMETHING TO THINK ABOUT!!!!

EXCITED ATOMS

AND

THE FOURTH

OF

JULY!!!!!


Atomic structure and electron configuration

Dalton's Atomic Theory

  • 1) All matter is made of atoms. Atoms are indivisible and indestructible.

  • 2) All atoms of a given element are identical in mass and properties

  • 3) Compounds are formed by a combination of two or more different kinds of atoms.

  • 4) A chemical reaction is a rearrangement of atoms.


Atomic structure and electron configuration

Law of definite proportions

Sometimes called Proust's Law, states that a chemical compound always contains exactly the same proportion of elements by mass. An equivalent statement is the law of constant composition, which states that all samples of a given chemical compound have the same elemental composition by mass. For example, oxygen makes up about 8/9 of the mass of any sample of pure water, while hydrogen makes up the remaining 1/9 of the mass.


Atomic structure and electron configuration

LAW OF CONSERVATION OF MASS

  • Definition: Law of Conservation of Mass is a relation stating that in a chemical reaction, the mass of the products equals the mass of the reactants.

    DEFINITION OF MULTIPLE PROPORTIONS

  • two elements can combine to form more than one compound, the ratio by weight of one element to a given weight of the second is usually a small whole number

  • EXAMPLES: NO2, NO, N2O or H2O, H2O2.


Atomic structure and electron configuration

ATOMIC MASS:

  • The simplest explanation for what is atomic mass unit is that it is equal to 1/12 of a carbon 12 atom. You might see an atomic mass unit called by it's other name--a dalton.

    MOLE - SI unit for amount

    AVOGADRO’S CONSTANT:

  • the number of particles, 6.022 X 10 23,

    in exactly 1 mole of a pure substance.


Parts of an atom

PARTS OF AN ATOM

NUCLEUS – Gold Foil Experiment

Protons - positively charged particles

Neutrons – neutrally charged particles

ELECTRON CLOUD – Cathode Ray Tube

Electrons – Negatively charged

particles


What is the internal structure of atoms

WHAT IS THE INTERNAL STRUCTURE OF ATOMS?

ELECTRON

J. J. Thomson was born in a suburb

of Manchester, England, in 1856.

He studied mathematics at Trinity

College and became a professor

there. His pioneering research into

the nature of cathode rays led to

his discovery of the electron. He won the Nobel Prize

in physics in 1906, and was knighted in 1908. He died

in Cambridge in 1940.


Atomic structure and electron configuration

J J Thomson Research – Electron

In 1894, Thomson began studying cathode rays, which are glowing beams of light that follow an electrical discharge in a high-vacuum tube. It was a popular research topic among physicists at the time because the nature of cathode rays was unclear.

Thomson devised better equipment and methods than had been used before. When he passed the rays through the vacuum, he was able to measure the angle at which they were deflected and calculate the ratio of the electrical charge to the mass of the particles. He discovered that the ratio was the same regardless of what type of gas was used, which led him to conclude that the particles that made up the gases were universal. He determined that all matter is made up of tiny particles that are much smaller than atoms. He originally called these particles 'corpuscles,' although they are now called electrons. This discovery upended the prevailing theory that the atom was the smallest fundamental unit.


Atomic structure and electron configuration

J J Thomas’s Cathode Ray Experiment Setup


Atomic structure and electron configuration

Ernest Rutherford

was born on August 30, 1871, in Nelson, New Zealand,

the fourth child and second son in a family of seven sons

and five daughters. His father James Rutherford, a

Scottish wheelwright, emigrated to New Zealand with

Ernest's grandfather and the whole family in 1842.

His mother was an English schoolteacher, who, with

Her widowed mother, also went to live there in 1855.Ernest received his early education in Government

schools and at the age of 16 entered Nelson Collegiate School.

In 1889 he was awarded a University scholarship and he

proceeded to the University of New Zealand, Wellington,

where he entered Canterbury College*. He graduated M.A. in

1893 with a double first in Mathematics and Physical Science

and he continued with research work at the College for a short

time, receiving the B.Sc. degree the following year. That same year, 1894, he was awarded an 1851 Exhibition Science Scholarship,


Atomic structure and electron configuration

Before Ernest Rutherford's landmark experiment with a few pieces of metal foil and alpha particles, the structure of the atom was thought to correspond with the plum pudding model. In summary, the plum pudding model was hypothesized by J.J. Thomson (the discoverer of the electron) who described an atom as being a large positively charged body that contained small, free-floating, negatively charged particles called electrons. The plum pudding model also states that the negative charge of the electrons is equivalent to the positive charge of the rest of the atom. The two charges cancel each other causing and cause the electrical charge of the atom to be zero (or neutral). The faulty aspect of this model is that it was construed before the nucleus of an atom (and its composition) was discovered; which is where Rutherford's research comes in.


Atomic structure and electron configuration

  • Atomic Number:

    The number of protons in nucleus

  • Mass Number:

    The number of protons plus the number of neutrons

  • Isotopes:

    Atoms of the same element with different numbers of neutrons


Symbols can represent atomic sructures

SYMBOLS CAN REPRESENT ATOMIC SRUCTURES

  • Each element has a name and each atom of that element has the same name.

    Example: oxygen is composed of oxygen atoms

  • Each element has a symbol

    Example: O represents oxygen

  • To indicate numbers of atoms scientist use subscripts

    O2 two atoms of oxygen

  • Atomic number and mass number are sometimes written with an element’s symbol; sometimes indicating isotopes : page 88


Atomic structure and electron configuration

Coulomb’s Law:

The closer two charges come together, the greater the force between them.

  • If the charges have different signs, they attract one another. If the charges are alike, they repel one another.

  • Strong Force- helps overcome repulsion of same sign particles at close distances. Hence, protons and neutrons can form stable nuclei by strong forces.


Isotopes

ISOTOPES

  • ATOMS OF THE SAME ELEMENT WITH DIFFERENT NUMBERS OF NEUTRONS

    Helium-3Helium-4

    Number of protons always the same

    Number of electrons-always the same

    Number of neutrons differ

    atomic mass (decimal number on Periodic table)


Let s try it

Let’s try it

  • PAGE 90

  • Section Review:

    • 1, 2, 3, 5, 7


Electron configurations

ELECTRON CONFIGURATIONS

  • electromagnetic wave: example Light

  • Three parts to these waves:

    speed, wavelength, frequency

    Speed- speed of light : 2.998 X 108m/s. (с)

    Wavelength- distance between two consecutive peaks or troughs in a wave. ()

    Frequency- number of waves that pass a stationary point.( γ )

    frequency x wavelength = speed of light


Atomic structure and electron configuration

Page 95: Figure 3-23

GROUND STATE- lowest energy state of quantized energy

EXCITED STATE- atom in a higher energy state

QUANTUM NUMBER- a number with certain definite values.

ORBITALS- a region of an atom in which there is a high probability of finding one or more electrons.

s, p, d, f


Quantum numbers

QUANTUM NUMBERS

n = principal quantum number

energy level- 1,2,3,4,5,6,7

larger the number- farther the orbit is out

l = indicates orbit e- is located, n→ n−1

so if n=1, then l=0 or 1.

l = 0 corresponds to s orbital

l = 1 ῎῎῎ p orbital

l = 2 d orbital

l = 3 f orbital


Atomic structure and electron configuration

m = dependent on l quantum number

whole number value

l = 1 then m = -1, 0, 1 ( p orbital)

l = 2 then m = -2, -1, 0, 1, 2 (d orbital)

  • l and m quantum numbers designate the shape and the orientation of the orbitals

    ms= spin quantum number, +1/2 or -1/2

    Quantum theory tells us exact energy of the e-, but only the probability that the e- will be in that particular region.


Atomic structure and electron configuration

Page 98 in text shows shapes of orbitals

  • Pauli’s exclusion principle- up to two e- can occupy the same orbital . If 2 e- do occupy the same orbital, they must have different spins.

  • Aufbau Principle- German word for “building up”

    e- fill the lowest energy orbitals first

    We know:

    • which orbitals are occupied

    • by how many e-

      This tells us the electron configuration of an atom.


Atomic structure and electron configuration

ELECTRON CONFIGURATIONS

1. Determine the total number of electrons an atom possesses.

2. Fill orbitals in order of increasing energy.

3. Make sure the total number of electrons in the electron configuration equals the atomic number. *as long as it’s not an ion

Let’s try a few!!!!!

Sc, K, P, B, In, Ba


Atomic structure and electron configuration

HOMEWORK

PAGE 101 #1-8


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