The Periodic Table

Periodic Table Dmitri Mendeleev ( ) "We could live at the present day without a Plato, but a double number of Newtons is required to discover the secrets of nature, and to bring life into harmony with the laws of nature."

Modern Periodic Table

s- and p-orbitals ‘Aufbau’ Principle: filling orbitals 1s2s2p n = 1 l = 0 m l = 0 n = 2 l = 0 m l = 0 n = 2 l = 0 m l = 0m l = 1m l = -1 H: 1s 1

s- and p-orbitals ‘Aufbau’ Principle: filling orbitals 1s2s2p n = 1 l = 0 m l = 0 n = 2 l = 0 m l = 0 n = 2 l = 0 m l = 0m l = 1m l = -1 He: 1s 2

s- and p-orbitals ‘Aufbau’ Principle: filling orbitals 1s2s2p n = 1 l = 0 m l = 0 n = 2 l = 0 m l = 0 n = 2 l = 0 m l = 0m l = 1m l = -1 Li: 1s 2 2s 1

s- and p-orbitals ‘Aufbau’ Principle: filling orbitals 1s2s2p n = 1 l = 0 m l = 0 n = 2 l = 0 m l = 0 n = 2 l = 0 m l = 0m l = 1m l = -1 Be: 1s 2 2s 2

s- and p-orbitals ‘Aufbau’ Principle: filling orbitals 1s2s2p B: 1s 2 2s 2 2p 1 ‘core’ closed shell open shell: valence electrons

s- and p-orbitals ‘Aufbau’ Principle: filling orbitals Hund’s rule: maximum number of unpaired electrons is the lowest energy arrangement. 1s2s2p C: 1s 2 2s 2 2p 2

s- and p-orbitals ‘Aufbau’ Principle: filling orbitals 1s2s2p N: 1s 2 2s 2 2p 3 O: 1s 2 2s 2 2p 4

s- and p-orbitals ‘Aufbau’ Principle: filling orbitals 1s2s2p F: 1s 2 2s 2 2p 5 Ne: 1s 2 2s 2 2p 6

s- and p-orbitals ‘Aufbau’ Principle: filling orbitals Na: 1s 2 2s 2 2p 6 3s 1 or [Ne]3s 1 Mg: 1s 2 2s 2 2p 6 3s 2 or [Ne]3s 2 P: [Ne]3s 2 3p 3 Ar: [Ne]3s 2 3p 6

d-orbitals E 1s 2s 3s 4s 2p 3p 3d Due to deeper penetration of s-orbitals, 4s lies lower in energy than 3d

d-orbitals K: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 or [Ar]4s 1 Ca: [Ar]4s 2 Sc: [Ar]4s 2 3d 1 V: [Ar]4s 2 3d 3 Cr: [Ar]4s 1 3d 5 Co: [Ar]4s 2 3d 7 Cu: [Ar]4s 1 3d 10 Zn: [Ar]4s 2 3d 10 Ga: [Ar]4s 2 3d 10 4p 1 Kr: [Ar]4s 2 3d 10 4p 6

Beyond the d-orbitals lanthanides actinides ‘s’-groups ‘p’-groups d-transition elements f-transition elements

Aufbau rules 1. Within a shell (n) the filling order is s>p>d>f 2. Within a subshell (l), lowest energy arrangement has the highest number of unpaired spin (Hund’s rule) 3. The (n+1)s orbitals always fill before the nd orbitals 4. After lanthanum ([Xe]6s 2 5d 1 ), the 4f orbitals are filled 5. After actinium ([Rn]7s 2 6d 1 ), the 5f orbitals are filled Filled subshells accommodate: s:2 electrons p:6 electrons d:10 electrons f:14 electrons

Electron configuration Give the electron configuration of Zirconium and Tellurium. Identify the period and the group of the element Zirconium is in period 5 and is the 2nd element in the d-transition element group. Zr: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 2 or [Kr]5s 2 4d 2 Tellurium is in period 5 and is the 4th element in the ‘p’- group. Te: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 4 or [Kr]5s 2 4d 10 5p 4

Exotic elements Elements with atomic numbers higher than 92 (Uranium) typically don’t exist in nature and have to be made by nuclear synthesis The first synthesized elements were named after the planets: uranium neptunium plutonium Ur 92 Np 93 Pu 94

Exotic elements Md 101 Mendelevium Es 99 Einsteinium Bh 107 Bohrium Lives for only 10 ms! Uun 110 No name yet! Barbarium?

Atomic Radius The atomic radius r is usually determined from the distances between atoms in covalent bonds. How big is an atom? Atomic radius decreases across a period from left to right due to increased effective nuclear charge Atomic radius increases down a group because of the larger sizes of the orbitals with higher quantum numbers.

Atomic Radius

Covalent radius is much smaller than the anionic radius.

Atomic Radius Arrange the following sets of atoms in order of increasing size: Sr, Se, Ne : Fe, P, O : Ne(10) < Se(34) < Sr(38) O(8) < P(15) < Fe(26) Li + (3) < Na + (11) < Rb + (37) Arrange the following sets of ions in order of increasing size: Na +, Rb +, Li + : Cl -, F -, I - : F - (9) < Cl - (17) < I - (53)

Ionization Energy Ionization energy is the energy required to remove an electron from a gaseous atom or ion : e-e- + X(g) X + (g) + e - S(g) S + (g) + e - I 1 = kJ/mol 1st ionization energy S + (g) S 2+ (g) + e - I 2 = 2251 kJ/mol 2nd ionization energy S 2+ (g) S 3+ (g) + e - I 3 = 3361 kJ/mol 3rd ionization energy

Ionization Energy S(g) S + (g) + e - I 1 = kJ/mol 1st ionization energy S + (g) S 2+ (g) + e - I 2 = 2251 kJ/mol 2nd ionization energy S 2+ (g) S 3+ (g) + e - I 3 = 3361 kJ/mol 3rd ionization energy S: 1s 2 2s 2 2p 6 3s 2 3p 4 Which electrons are removed in successive ionizations? Electrons in the outer subshells take the least amount of energy to remove (valence electrons) It takes about kJ/mol to remove successive electrons from the 3p shell of sulfur.

Ionization Energy Ionization energies of aluminum: Al(g) Al + (g) + e - I 1 = 580 kJ/mol 1st ionization energy Al + (g) Al 2+ (g) + e - I 2 = 1815 kJ/mol 2nd ionization energy Al 2+ (g) Al 3+ (g) + e - I 3 = 2750 kJ/mol 3rd ionization energy Al 3+ (g) Al 4+ (g) + e - I 4 = 11,600 kJ/mol 4th ionization energy Al: 1s 2 2s 2 2p 6 3s 2 3p 1 1st electron: 3p valence electron 2nd electron: 3s valence electron 3rd electron: 3s valence electron 4th electron: 2p core electron! core electrons take much more energy to remove

Ionization Energy

First ionization energies Ionization energy increases across the period from left to right. Ionization energy decreases going down a group General trends:

Ionization Energy A closer look….. B: 1s 2 2s 2 2p 1 O: 1s 2 2s 2 2p 4 New subshell, electron is easier to remove. First paired electron in 2p orbital: repulsion.

Understanding a group Atoms in a group have the same valence electron configuration and share many similarities in their chemistry. Group 1A: Alkali metals K NaLi Cs

Understanding a group Trends down the group reflect periodic changes in mass, volume and charge. Group 1A: Alkali metals

Periodic Table in Brief

Periodic Table Redux