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Compare Lead vs Thallium

Comparing Lead (Pb) and Thallium (Tl). Atomic numbers 82 and 81 with atomic masses 207.21 u and 204.382 u, classified as post-transition metal and post-transition metal. Below: a side-by-side comparison of their physical, atomic, electron-configuration and historical properties, including density, melting and boiling points, ionization energies, oxidation states and discovery history.

vs
Pb
Lead
#82
Tl
Thallium
#81

Periodic properties of the elements

LeadThallium
SymbolPbTl
Atomic number8281
Group1413
Period66
Blockpp
Element categoryPost-Transition MetalPost-Transition Metal

Physical properties

LeadThallium
Phase at STPSolidSolid
Density11.34 g/cm311.85 g/cm3
Atomic weight207.21 u204.382 u
Melting point600.61 K
327.46 °C
621.428 °F		577 K
303.85 °C
578.93 °F
Boiling point2022 K
1748.85 °C
3179.93 °F		1746 K
1472.85 °C
2683.13 °F

Atomic properties

LeadThallium
Electronegativity (Pauling Scale)1.871.62
Electron affinity34.4204 kJ/mol36.4 kJ/mol
Oxidation states−4, −2, −1, +1, +2, +3, +4
(an amphoteric oxide)		−5, −2, −1, +1, +2, +3
(a mildly basic oxide)
Ionization energies
  1. 715.6 kJ/mol
  2. 1450.5 kJ/mol
  3. 3081.5 kJ/mol
  4. 4083 kJ/mol
  5. 6640 kJ/mol
  1. 589.4 kJ/mol
  2. 1971 kJ/mol
  3. 2878 kJ/mol

Electron configuration

LeadThallium
Shorthand configuration[Xe] 4f14 5d10 6s2 6p2 [Xe] 4f14 5d10 6s2 6p1
Full configuration1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p2 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p1
Electrons per shell2, 8, 18, 32, 18, 42, 8, 18, 32, 18, 3

History

LeadThallium
DiscoveryAncient Near East (7000 BC)William Crookes (1861)
First isolationClaude-Auguste Lamy (1862)
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