atomic theory p
DESCRIPTION
A set of slides created to teach Atomic Theory P to learners at Bishops Diocesan College in Cape Town.TRANSCRIPT
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
………………………..
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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
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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
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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