Periodic Relationships Among the Elements When the Elements

Periodic Relationships Among the Elements

When the Elements Were Discovered 2

4 f 5 f 3 ns 2 np 6 ns 2 np 5 ns 2 np 4 ns 2 np 3 ns 2 np 2 ns 2 np 1 d 10 d 5 d 1 ns 2 ns 1 Ground State Electron Configurations of the Elements

Classification of the Elements 4

Electron Configurations of Cations and Anions Of Representative Elements Na [Ne]3 s 1 Na+ [Ne] Ca [Ar]4 s 2 Ca 2+ [Ar] Al [Ne]3 s 23 p 1 Al 3+ [Ne] Atoms gain electrons so that anion has a noblegas outer electron configuration. Atoms lose electrons so that cation has a noble-gas outer electron configuration. H 1 s 1 H- 1 s 2 or [He] F 1 s 22 p 5 F- 1 s 22 p 6 or [Ne] O 1 s 22 p 4 O 2 - 1 s 22 p 6 or [Ne] N 1 s 22 p 3 N 3 - 1 s 22 p 6 or [Ne] 5

-1 -2 -3 +3 +1 +2 Cations and Anions Of Representative Elements 6

Isoelectronic: have the same number of electrons, and hence the same ground-state electron configuration Na+: [Ne] Al 3+: [Ne] O 2 -: 1 s 22 p 6 or [Ne] F-: 1 s 22 p 6 or [Ne] N 3 -: 1 s 22 p 6 or [Ne] Na+, Al 3+, F-, O 2 -, and N 3 - are all isoelectronic with Ne What neutral atom is isoelectronic with H- ? H-: 1 s 2 same electron configuration as He 7

Electron Configurations of Cations of Transition Metals When a cation is formed from an atom of a transition metal, electrons are always removed first from the ns orbital and then from the (n – 1)d orbitals. Fe: [Ar]4 s 23 d 6 Fe 2+: [Ar]4 s 03 d 6 or [Ar]3 d 6 Mn: [Ar]4 s 23 d 5 Mn 2+: [Ar]4 s 03 d 5 or [Ar]3 d 5 Fe 3+: [Ar]4 s 03 d 5 or [Ar]3 d 5 8

Atomic Radii metallic radius covalent radius 9

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Trends in Atomic Radii 11

Ionization energy is the minimum energy (k. J/mol) required to remove an electron from a gaseous atom in its ground state. I 1 + X (g) X+(g) + e- I 1 first ionization energy I 2 + X+(g) X 2+(g) + e- I 2 second ionization energy I 3 + X 2+(g) X 3+(g) + e- I 3 third ionization energy I 1 < I 2 < I 3 12

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Variation of the First Ionization Energy with Atomic Number Filled n=1 shell Filled n=2 shell Filled n=3 shell Filled n=4 shell Filled n=5 shell 14

General Trends in First Ionization Energies Increasing First Ionization Energy 15

Electron affinity is the negative of the energy change that occurs when an electron is accepted by an atom in the gaseous state to form an anion. X (g) + e- X-(g) F (g) + e- X-(g) DH = -328 k. J/mol EA = +328 k. J/mol O (g) + e- O-(g) DH = -141 k. J/mol EA = +141 k. J/mol 16

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Variation of Electron Affinity With Atomic Number (H – Ba) 18