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Topic 12

Topic 12. Atomic Structure HL. 12.1 Electron Configuration . Studies of the I onisations E nergies going across a period and down a group IE- The energy required to remove an elektron from an atom or ion Orbitals. K L M N. 1 st IE: A (g) + energy  A (g) + + e - (g)

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Topic 12

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  1. Topic 12 Atomic Structure HL

  2. 12.1 Electron Configuration • Studies of the Ionisations Energies going across a period and down a group • IE- The energy required to remove an elektron from an atom or ion • Orbitals

  3. K L M N 1st IE: A(g) + energy  A(g)+ + e-(g) 2nd IE: A(g)+ + energy A(g)2+ + e-(g) • Withinan energy level (shell or orbital): increased nuclear attraction => Increase in IE Nucleus + + - Energy Electron

  4. Successiveionisationenergies • If removed from inner filled levels: • electrons experience a much higher effective nuclear charge => • largeraise in ionisation energy.

  5. Variation of I.E. across a period: • Going across a period the I.E. increase. Increased charge of the nucleus increases the effective nuclear charge and the removed electrons are on the same energy level.

  6. Orbitals • The orbitals are solutions to the wave-equation. They depict the probability of where the electron can be within 90 % probability • Each orbital contains maximum 2 electrons • The different orbital shapes are called s, p, d, f, g.

  7. S-orbital: sphere formelectrons fill up S-orbitals in group 1 and 2K-shell: 1s , L-shell: 2s , M-shell: 3s

  8. p-orbitalsdumbbell form Three at each energy level except level 1. They are called px, py, pzand are orientated in three different directions in space electrons fill up p-orbitals in groups 13-18L-shell: 2p , L-shell: 3p

  9. d-orbitals Five at each energy level except level 1 and 2. They are orientated in three different directions in space. Electrons fill up d-orbitals in group 4-12 (transition elements)M-shell: 3d , N-shell: 4d , O-shell: 5d

  10. f-orbitals Seven at each energy level except level 1, 2 and 3. They are orientated in three different directions in space. Electrons fill up f-orbitals for the lanthanoids and actiniods N-shell: 4f , O-shell: 5f

  11. Each orbital can just be occupied by twoelectrons. And the electrons must have different spin (Pauli principle) • The relative energies:s<p<d<f

  12. Shells Energy level Orbital’s Number of e- K n=1 1s 2 L n=2 2s2p 8 M n=3 3s3p3d 18 N n= 4 4s4p4d4f 32

  13. The Aufbau principle • One s-orbital on an energy level • Three p-orbital’s on an energy level • Five d-orbital’s on an energy level • Seven f-orbital’s on an energy level

  14. Electrons always try to adopt the lowest energy configuration as possible. This is known as the “Aufbau principle” • The orbital in the different energy levels overlaps each other- “read” the periodic table • You should be able to apply the Aufbau principle for an atom up to Z = 54.

  15. Hund’s rule • When orbitals of identical energy are available, electrons occupy these singly rather than in pairs.

  16. Electronic configuration of ; • 6C: 1s22s22p2 • 16S: 1s22s22p63s23p4 • The electronic configuration of atoms and their ions can be explained in a good way with the Aufbau principle.

  17. Formation of ions • Atoms like to have filled orbitals, almost as good as that is to have half filled orbitals. • Sometimes, i.e. Zn Zn2+, the atom throw away electrons on a lower level, 4s2, instead of breaking the full 3d10 on the higher energy level => all orbitals are filled. • Also for Cr and Cu => 4s2 => 4s1 and e- to d-orbitals to make half-filled and filled orbitals

  18. Back to variation of I.E. across a period: • Going across a period the I.E. increase. Increased charge of the nucleus increases the effective nuclear charge and the removed electrons are on the same energy level. But: • From second to third element decrease: Electron removed from p-orbital instead of s-orbital. • From fifth to sixth element decrease: In fifth orbital's are singly filled, in sixth one is doubly filled => higher repulsion.

  19. If removed from inner filled level: electrons experience a much higher effective nuclear charge => large raise in ionisation energy.

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