Atomic Theory P

THE ATOM

Atomic Theory

GRADE 10 K WARNE

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Rutherford’s experiment

• Rutherford shot ................... particles at very thin gold foil.

• Most of the radiation ........................................

• Some radiation was .................................. - by significant amounts.

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Atomic Structure Revision

ELEMENT SYMBOL Z (ATOMIC

NUMBER)

A (MASS

NUMBER)

NEUTRONS ELECTRONS

TOT VALENCE

Hydrogen H 1 1 0 1 1

Lithium Li 3 7 4 3 1

Carbon C 6 12 6 6 4

Nitrogen N 7 14 7 7 5

O

Ne

Na

Ar

Ca

Fill in the missing information for each of the elements above – note any

patterns that begin to develop.

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THE NEUTRAL ATOM

Notation

Z

A

XAtomic Number

(smaller)

Mass Number

(bigger) symbol

• Atomic Number Z = number of protons (& electrons)

• Mass number A = protons + neutrons.

• Number of neutrons = A - Z

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Atomic SpectraA glass prism can be used

to generate a colour

…………………..

If this the light generated

by a hot (glowing) gas is

viewed through a prism

specific colour lines are

seen as AN ………………

………….SPECTRUM.

If light is shone through a

cold sample of the same

gas, the same specific

colour lines are absent

and appear as an

………………………..

LINE SPECTRUM. 5SAMPLE ONLY

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Absorption & Emission spectrum

• In absorption spectrum radiation is again absorbed by

electrons being …………… to higher energy levels.

• The same frequencies (colours) are again emitted when the

excited electrons ……………………. to the ground state

in an ………………………spectrum.

---- …………………………………………………

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Bohr’s Atom - problems• Only explain hydrogen

spectrum.

• Could not explain molecules (bonding of atoms) -formation or properties.

• Why fixed orbits and no energy radiation in orbits.

• At variance with Heisenberg’s uncertainty principle.

Heisenberg: Not possible to know both the position and velocity of an electron at

the same time with the same amount of accuracy.

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Bohr Orbits -

energy levels

N = 4

N = 3

N = 2

N = 1

Electron StructureEnergy sub levels and orbitals

1s orbital

2s

2p orbitals3s

3p orbitals

4s

4p (3d

orbitals)

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Ei Trends in a group

4s

3s

2s

1s

3p

2p

Li 1s2 2s1

4s

3s

2s

1s

3p

2p

Na 1s2 2s2 2p6 3s1

OUTER ELECTRON FURTHER

FROM NUCLEUS – LESS

ENERGY REQUIRED TO

REMOVE IT – LOWER EI1

COMPLETE INNER LEVELS SHIELD THE OUTER

ELECTRONS FROM THE EFFECTS OF THE

INCREASED NUCLEAR CHARGE

3 PROTONS 11 PROTONS

FIRST Ei DECREASES DOWN A

GROUP!

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Successive Ionization EnergiesFIRST ionisation energy (Ei1): Energy required to remove OUTERMOST

electron. M M+ + 1e-

SECOND ionisation energy (Ei2): Energy required to remove SECOND

OUTERMOST electron. M+ M2+ + 1e-

Inner

level

Hard to

remove

close to

nucleus

Second energy

level

Outer

(valence)

level

Easy to

remove far

from the

nucleus

This graph provides EVIDENCE for energy levels.10






FIRST ionisation energy (Ei1): Energy required to remove OUTERMOST

electron. M M+ + 1e-

Patterns in First Ionization Energies (Ei1)

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Isotopes

Isotopes

Atoms of the same element which have different numbers ofneutrons. Others – Boron 10 & 11, Hydrogen 1 & 2, Chlorine 35 & 37. Write notation and work out numbers of neutrons.

e- e-

e- e-e-

e-e- e

-

e- e-e-

e-

The two atoms below both belong to carbon but they are not identical – can

you spot what is different?

612C 6

13C

510B 511B 17

35Cl 1737Cl 1

1H 12H12






Isotopes

• Isotopes - Atoms of the _______________ which

have different _____________________________________.

Eg: 613C & 6

12C

• 37Cl (25%) & 35Cl (75%) - ratio _________

Av Ar(Cl) =

Or

Av Ar(Cl) =

Relative atomic mass is (actually) the ____________ mass of an atom of an elementrelative to 1/12 of the mass of a carbon-twelve atom.

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THE NEUTRAL ATOM• The atom consists of a _____________________

______________________________ surrounded by a

__________________________.

• Atomic Number Z: ___________________ in the Nucleus =

_________________ in a ______ atom.

• Mass number A - Number of ______ + ________

Notation

Z

A

X______________ Number

(smaller)

___________ Number

(bigger) symbol

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Hi -

This is a SAMPLE presentation only.

My FULL presentations, which contain a lot more more slides and other resources, are freely

available on my resource sharing website:

www.warnescience.net(click on link or logo)

Have a look and enjoy!

WarneScience






Education

Atomic Theory P