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Atomic Theory. Everything written in black has to go into your notebook Everything written in blue should already be in there. Atom : Smallest part of any element, which can take part in a chemical reaction Element : Pure substance consisting of one type of atom only

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Atomic theory

Atomic Theory

Everything written in black has to go into your notebook

Everything written in blue should already be in there


  • Atom: Smallest part of any element, which can take part in a chemical reaction

  • Element: Pure substance consisting of one type of atom only

  • Compound: Substance consisting of two or more elements (e.g. H2O)

  • Mixture: Consists of two or more substances but they are not joined together chemically (e.g. sand and iron filings)


Molecule: Smallest part of a substance which can exist on its own (e.g. Cu, H2, H2O)

  • There are monatomic, diatomic or triatomic molecules


1 a.m.u. = 1.66 x 10-27 kg


The bohr model
The Bohr Model

Protons and neutrons are located in the nucleus of the atom

Electrons orbit the nucleus in ‘shells’ or ‘energy levels’


1st energy level can hold 2 electrons

2nd energy level can hold 8 electrons

3rd energy level can hold 18 electrons


7

3

3P 4N

E.g. Lithium Li


23

11

11P 12N

E.g. sodium Na


  • Isotopes: Atoms with the same number of protons but different numbers of neutrons (e.g. carbon 12, carbon 13 and carbon 14)


  • Isotopes: Atoms having the same number of protons but different numbers of neutrons (e.g. carbon 12, carbon 13 and carbon 14)

  • Atomic Number (Z): The number of protons in an atom

  • Mass Number (A): The number of protons and neutrons in an atom

  • Relative atomic mass: The mass of an atom compared to of the mass of an atom of carbon




E out by excited atoms of an element2

Higher energy level

Photon of light emitted

Lower energy level

E1


E out by excited atoms of an element2 – E1 = hf

E2 = energy of electron in higher energy level

E1 = energy of electron in lower energy level

h = Planck’s constant

f = frequency of light emitted


Flame tests page 126
Flame tests (page 126) out by excited atoms of an element


The ground state is the energy level of the electron before it gains energy

The excited state is the energy level of the electron after it gains energy


The aufbau principal
The Aufbau Principal it gains energy

  • Electrons always fill the lowest energy level available when the atom is in the ground state

  • Remember that lower energy levels are nearer the nucleus, and higher energy levels are further away from the nucleus


2 it gains energy

8

18

  • 1st shell (n =1) holds up to electrons

  • 2nd shell (n=2) holds up electrons

  • 3rd shell (n=3) holds up to electrons

  • 4th shell (n=4) holds up to electrons

  • Each of these main energy levels (shells) contains “sub-levels”

32


Consider it like 5 it gains energyth year is split into 3 classes; so an energy level is split into ‘sub-energy levels’


4f it gains energy

4d

N=4

4p

s holds 2

p holds 6

d holds 10

f holds 14

4s

3d

N=3

3p

3s

2p

N=2

2s

N=1

1s


They are filled in this order
They are filled in this order it gains energy

4f

4d

4p

3d

3d “jumps” up!

4s

3p

3s

2p

2s

1s


Writing electronic configurations
Writing electronic configurations: it gains energy

Example 2

Cobalt (Co)

1s2 2s2 2p6 3s2 3p6 4s2 3d7


  • Copper it gains energy and chromium are the only exceptions to the trend


  • 1s it gains energy2, 2s2, 2p6, 3s2, 3p6, 4s2,

4s1, 3d5

3d4


  • 1s it gains energy2, 2s2, 2p6, 3s2, 3p6, 4s2,

4s1, 3d10

3d9


Atomic orbitals
Atomic Orbitals it gains energy

  • An atomic orbital is the region around a nucleus where there is a high probability of finding an electron


Main energy level it gains energy

Atomic orbitals

Sub-level

s

s

px

py

pz


s it gains energy

s

px

py

pz


s it gains energy

s

px

py

pz

s

px

py

pz



S sub level has 1 orbital
s sub-level has 1 orbital it gains energy

  • spherical in shape


P sub level has 3 orbitals
p sub-level has 3 orbitals it gains energy

  • dumb bell shape

px py pz



Hund s rule of maximum multiplicity
Hund’s Rule of Maximum Multiplicity it gains energy

  • When two or more orbitals of equal energy are available to electrons the electrons occupy them singly, before filling them in pairs

Sometimes called the“Bus Seat Rule”


Pauli s exclusion principle
Pauli’s Exclusion Principle it gains energy

  • No more than two electrons can occupy an orbital, and they can only do this if they have opposite spin


Example
Example it gains energy

  • Oxygen

  • O


1s 2 2s 2 2p 4
1s it gains energy2 2s2 2p4


Quantum numbers
Quantum Numbers it gains energy

  • A code consisting of 4 numbers, which give the full information about any one electron in an atom


Question
Question it gains energy

  • Give the 4 quantum numbers for each of the electrons in the Berylium atom


electronic configuration: 1s it gains energy2 2s2

1st electron: 1, 0, 0, ½

2nd electron: 1, 0, 0, -½

3rd electron: 2, 0, 0, ½

4th electron: 2, 0, 0, -½


The periodic table
The Periodic Table it gains energy

  • Groups go from top to bottom

  • Elements in the same group have the same number of electrons in their outer shell, and so have similar chemical properties

  • NB: Group 1 (Alkali metals)

  • Group 2 (Alkaline earth metals)

  • Group 7 (Halogens)

  • Group 8 (Noble gases)



A group is a vertical column in the Periodic Table it gains energy

A period is a horizontal row in the Periodic Table


Valency
Valency it gains energy

The number of electrons that one atom of that element will give, take or share when it forms a chemical bond


Metals and non metals
Metals and Non-Metals it gains energy

  • The periodic table may be divided up into metals and non-metals

  • Metals are hard, shiny, and good conductors of electricity

  • Carbon exhibits properties of both metals and non-metals


Transition elements d block elements
Transition Elements (d-block elements) it gains energy

  • They are all metals

  • They act as catalysts

  • They form coloured compounds

  • They have an incomplete d subshell

  • They have variable valency

    • E.g. Copper, 1 or 2

    • Iron, 2 or 3


Ionisation energy
Ionisation Energy it gains energy

  • The ionisation energy of an element is the minimum energy required to remove the outermost electron from a neutral gaseous atom

  • The ionisation energy is the minimum energy required to remove the outermost electron from an atom

HL

OL





Full s sublevel because

  • Be: 1s2, 2s2

  • Mg: 1s2, 2s2, 2p6, 3s2

  • N: 1s2, 2s2, 2p3

  • P: 1s2, 2s2, 2p6, 3s2, 3p3

  • Their outer sub-energy levels are full so they are stable

Half-full p sublevel


Second ionisation energy
Second Ionisation Energy because

  • The second ionisation energy of an element is the minimum energy required to remove the second outermost electron from a neutral gaseous atom

  • The second ionisation energy is the minimum energy required to remove the second outermost electron from an atom

HL

OL


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