Cadmium (Cd)

Element 48 · transition metal · group 12, period 5

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

Cadmium is element 48, a transition metal in group 12 and period 5. Its electron configuration is [Kr] 4d10 5s2. The shells fill 2, 8, 18, 18, 2. Courses differ here. Counting only the outer s subshell gives 2; counting the inner d subshell with it gives 12, which is the group number. It commonly forms ions with a charge of +2.

48 protons
2/12 valence e−
+2
d-block

Properties

Atomic number	48
Symbol	Cd
Standard atomic weight	112.41 u
Group	12
Period	5
Block	d-block
Category	transition metal
Electron configuration	1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s²
Noble-gas notation	[Kr] 4d¹⁰ 5s²
Electrons per shell	2, 8, 18, 18, 2
Valence electrons	2 or 12
Common ionic charge	+2
Electronegativity (Pauling)	1.69
Protons / electrons	48 / 48

Electron configuration of cadmium

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

Everything up to Kr is the same as in that noble gas, so it is usually abbreviated to [Kr] 4d¹⁰ 5s². 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

Cadmium ion charge

Cadmium commonly forms ions with a charge of +2.

Common questions

How many valence electrons does cadmium have?

There is no single agreed answer for cadmium. Courses differ here. Counting only the outer s subshell gives 2; counting the inner d subshell with it gives 12, which is the group number. Check which convention your course uses before answering.

What is the electron configuration of cadmium?

1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2, or [Kr] 4d10 5s2 written from the previous noble gas. Orbitals fill lowest energy first.

What is the charge of cadmium?

Cadmium commonly forms ions with a charge of +2. Transition metals have several accessible oxidation states, which is why more than one charge is listed.

How many protons, electrons and neutrons does cadmium have?

A neutral cadmium atom has 48 protons and 48 electrons. Its standard atomic weight is 112.41, so the most common isotope has about 64 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 48 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.