Lanthanum (La)

Element 57 · lanthanide · group 3, period 6

Electron shells, 2 + 8 + 18 + 18 + 9 + 2. The outer shell is highlighted - it is the only one that takes part in bonding.

Lanthanum is element 57, a lanthanide in group 3 and period 6. Its electron configuration is [Xe] 5d1 6s2. The shells fill 2, 8, 18, 18, 9, 2. The f-block elements draw on three subshells, so a single valence count is not meaningful for them. It commonly forms ions with a charge of +3.

57 protons
2/3 valence e−
+3
f-block

Properties

Atomic number	57
Symbol	La
Standard atomic weight	138.91 u
Group	3
Period	6
Block	f-block
Category	lanthanide
Electron configuration	1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s²
Noble-gas notation	[Xe] 5d¹ 6s²
Electrons per shell	2, 8, 18, 18, 9, 2
Valence electrons	2 or 3
Common ionic charge	+3
Electronegativity (Pauling)	1.1
Protons / electrons	57 / 57

Electron configuration of lanthanum

Orbitals fill from the lowest energy upward. Writing that out for lanthanum gives 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s², which is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 5d1 6s2 in plain text.

Everything up to Xe is the same as in that noble gas, so it is usually abbreviated to [Xe] 5d¹ 6s². The part outside the bracket is what does the chemistry.

Subshell	Electrons	Capacity
1s	2	2
2s	2	2
2p	6	6
3s	2	2
3p	6	6
3d	10	10
4s	2	2
4p	6	6
4d	10	10
5s	2	2
5p	6	6
5d	1	10
6s	2	2

Lanthanum ion charge

Lanthanum commonly forms ions with a charge of +3.

Common questions

How many valence electrons does lanthanum have?

There is no single agreed answer for lanthanum. The f-block elements draw on three subshells, so a single valence count is not meaningful for them. Check which convention your course uses before answering.

What is the electron configuration of lanthanum?

1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 5d1 6s2, or [Xe] 5d1 6s2 written from the previous noble gas. Orbitals fill lowest energy first, but lanthanum is one of the elements that breaks that order - a half-filled or filled d subshell is stable enough to be worth borrowing an s electron for.

What is the charge of lanthanum?

Lanthanum commonly forms ions with a charge of +3. Transition metals have several accessible oxidation states, which is why more than one charge is listed.

How many protons, electrons and neutrons does lanthanum have?

A neutral lanthanum atom has 57 protons and 57 electrons. Its standard atomic weight is 138.91, so the most common isotope has about 82 neutrons.

See the ionic charge of every element →

How this page was produced. The configuration was built by filling orbitals in energy order from atomic number 57 alone, not looked up. The shell counts, the valence count and the charge all follow from it. Nothing on this page is written per element.