Electron Configuration of the Elements Hydrogen Emission Spectrum When hydrogen gas (H 2 ) is placed in a CRT and a high voltage electrical current passed.
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Slide 1
Slide 2
Electron Configuration of the Elements
Slide 3
Hydrogen Emission Spectrum When hydrogen gas (H 2 ) is placed
in a CRT and a high voltage electrical current passed through it,
the tube glows a violet colour. Johann Balmer
Slide 4
When viewed through a spectroscope (prism), we observe four
discrete lines and NOT a continuous spectrum:
Slide 5
When an electron in the ground state of H absorbs energy, it
gets promoted into a higher energy level. The electron is unstable
in this higher energy level.
Slide 6
When the electron falls back to the ground state, energy is
given off. This explains the bands of light emitted from a hydrogen
discharge tube.
Slide 7
Slide 8
Heres another way to look at it:
Slide 9
Hydrogen Emission Spectrum Electrons can only exist in certain
energy levels (n) n = 1, n = 2, n = 3, n = 4, etc Energy levels in
atom are quantized. This means that only certain E levels are
allowed.
Slide 10
Each E level has one or more sublevels called orbitals An
orbital is a region of space where there is a high probability of
finding an electron
Slide 11
Each orbital can hold a maximum of two electrons. Electrons in
an orbital will have opposite spin, designated (clockwise spin) or
(counterclockwise spin).
Slide 12
high probability ? Heisenberg Uncertainty Principle We cannot
simultaneously know the position and the momentum of an
electron
Slide 13
Back to orbitals... For n = 1 there is only one sublevel,
called an s orbital. Since this orbital is in the first energy
level, it is called a 1s orbital. s orbitals are spherical.
Slide 14
For n = 2 there are two sublevels: 2s orbital (one of these) 2p
orbital (three of these) a p orbital looks like this A set of three
p orbitals looks like this We refer to the individual p orbitals as
p x, p y, p z.
Slide 15
Lets put these orbitals together...
Slide 16
For n = 3 (the third energy level) there are three sublevels:
3s orbital (one of these) 3p orbital (three of these) 3d orbital
(five of thesesee next slide) NB. Each orbital holds a maximum of 2
electrons
Slide 17
The d-orbitals
Slide 18
A funky look at d-orbitals
Slide 19
Your bottom line with d-orbitals: There are five of them in
each set. eg. there are five 3d orbitals; five 4d orbitals, etc 2
electrons in each, for a maximum of 10 electrons How many columns
are in the Transition Metal block (d-block) in the periodic table?
10 columns in the transition metals (5x2).
Slide 20
For n = 4 (the fourth energy level) there are four sublevels:
4s orbital (one of these) 4p orbital (three of these) 4d orbital
(five of these) 4f orbital (seven of thesesee next slide)
Slide 21
f-orbitals
Slide 22
How do electrons fill orbitals? Aufbau Principle aka
Building-up Principle Electrons occupy orbitals beginning from the
lowest energy orbital (i.e. the orbital closest to the nucleus)
Start by filling 1s orbital How many electrons per orbital? Each
orbital can hold a maximum of two electronsof opposite spin, dont
forget
Slide 23
Here is the order in which orbitals are filled...
Slide 24
Note the peculiarity... 3s is followed by 3p, which is followed
by 4s, which is followed by 3d. There are others... (help is on the
way)
Slide 25
How do the electrons of 7 N fill the orbitals? 1s 2 2s 2 2p 3
Overall for 7 N: 1s 2 2s 2 2p 3
Slide 26
Hunds Rule More stable than...
Slide 27
Hunds Rule When filling p, d, f orbitals, pair electrons only
when necessary
Slide 28
Aufbau Principle Mnemonic Device
Slide 29
Lets write some electron configurations... 1 H 1s 1 2 He 1s 2 3
Li 1s 2 2s 1 4 Be 1s 2 2s 2 5 B 1s 2 2s 2 2p 1 6 C 1s 2 2s 2 2p 2
10 Ne 1s 2 2s 2 2p 6
In the Periodic Table, what is the connection between the
outermost electron configuration and family (column)? Alkali metals
end in s 1 Alkali earth metals end in s 2 Halogens end in p 5 Noble
Gases end in p 6
Slide 32
Groups (families) in PT
Slide 33
Putting it all together... To write the electron configuration
of any element, use the periodic table (play Battleship) and the
Aufbau Principle mnemonic device.
Slide 34
Write the complete electron configuration for 1s 2 2s 2 2p 6 3s
2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 1
____________________________________ [Kr] preceding noble gas only
49 In [Kr] 5s 2 4d 10 5p 1
Slide 35
Practice Write the electron configuration for each of the
following 15 P 15 P 1s 2 2s 2 2p 6 3s 2 3p 3 33 As [use noble gas
core abbreviated form] 33 As [Ar] 4s 2 3d 10 4p 3
Slide 36
more practice... 13 Al 13 Al 1s 2 2s 2 2p 6 3s 2 3p 1 26 Fe 26
Fe 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 44 Ru [ ] 44 Ru [Kr] 5s 2 4d
6 52 Te [ ] 52 Te [Kr] 5s 2 4d 10 5p 4
Slide 37
Exceptional Electron Configurations 1. Write the expected
electron configuration of 24 Cr [Ar]4s 2 3d 4 Actual electron
configuration is [Ar]4s 1 3d 5 Special stability associated with
half-filled p, d, f orbitals
Slide 38
Now write the electron configuration for 42 Mo 42 Mo [Kr] 5s 1
4d 5 Notice any similarity with Cr?
Slide 39
2. Write the expected electron configuration of 29 Cu: [Ar]4s 2
3d 9 Actual electron configuration is [Ar]4s 1 3d 10 In this way Cu
has completely filled 3 rd energy level (Copper is a very stable
metal)
Slide 40
Now write the electron configuration for silver ( 47 Ag) and
gold ( 79 Au). Use the noble gas core abbreviated forms. 47 Ag [Kr]
5s 1 4d 10 79 Au [Xe] 6s 1 4f 14 5d 10