Transcript of Electron Configuration of the Elements Hydrogen Emission Spectrum When hydrogen gas (H 2 ) is placed...
- 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
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- When viewed through a spectroscope (prism), we observe four
discrete lines and NOT a continuous spectrum:
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- 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.
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- 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.
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- Heres another way to look at it:
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- 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.
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- 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
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- Each orbital can hold a maximum of two electrons. Electrons in
an orbital will have opposite spin, designated (clockwise spin) or
(counterclockwise spin).
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- high probability ? Heisenberg Uncertainty Principle We cannot
simultaneously know the position and the momentum of an
electron
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- 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.
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- 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.
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- Lets put these orbitals together...
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- 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
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- The d-orbitals
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- A funky look at d-orbitals
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- 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).
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- 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)
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- f-orbitals
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- 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
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- Here is the order in which orbitals are filled...
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- 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)
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- 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
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- Hunds Rule More stable than...
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- Hunds Rule When filling p, d, f orbitals, pair electrons only
when necessary
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- Aufbau Principle Mnemonic Device
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- 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
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- 11 Na 11 Na 1s 2 2s 2 2p 6 3s 1 12 Mg 1s 2 2s 2 2p 6 3s 2 13 Al
1s 2 2s 2 2p 6 3s 2 3p 1 18 Ar 1s 2 2s 2 2p 6 3s 2 3p 6 19 K 1s 2
2s 2 2p 6 3s 2 3p 6 4s 1 20 Ca 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 21 Sc
1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 1
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- 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
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- Groups (families) in PT
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- Putting it all together... To write the electron configuration
of any element, use the periodic table (play Battleship) and the
Aufbau Principle mnemonic device.
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- 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
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- 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
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- 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
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- 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
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- Now write the electron configuration for 42 Mo 42 Mo [Kr] 5s 1
4d 5 Notice any similarity with Cr?
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- 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)
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- 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