Thallium (Tl)
[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹. 1 unpaired electron, period 6, group 13, p block.
Element or ion
Type a symbol, a name or an atomic number, add a charge such as Fe3+ or Cl-, or tap an element in the table. Orbitals fill from m = −l up, spin +½ first.
TlThallium, Z = 81, 204.38 u
[Xe] 4f14 5d10 6s2 6p1
In full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p¹
- Blockp block
- Period6
- Group13
- Valence3
- Unpaired1
- MagneticPara
Last electron 6p
- n6shell
- l1p subshell
- m−1orbital
- s+½spin up
Step by step
- Thallium has 81 electrons.
- Fill in (n + l) order: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p¹.
- Write the subshells in order of n: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p¹.
- Replace the xenon core with [Xe]: [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹.
Thallium (Tl): the numbers
| Atomic number | 81 |
|---|---|
| Atomic mass | 204.38 u |
| Period | 6 |
| Group | 13 |
| Block | p block |
| Valence electrons | 3 |
| Unpaired electrons | 1 |
| Magnetic | paramagnetic |
| Last electron | 6p: n = 6, l = 1, m = −1, s = +1/2 |
Thallium (Tl): quick answers
What is the electronic configuration of thallium?
Thallium has 81 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p¹, or [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹ in short.
How many unpaired electrons does thallium have?
Thallium has 1 unpaired electron, so it is paramagnetic. Put one electron in each box of a subshell before pairing (Hund’s rule) to see them.
What are the quantum numbers of the last electron of thallium?
The last electron goes into 6p: n = 6, l = 1, m = −1, s = +1/2. Orbitals fill from m = −l up, spin +½ first.