Technetium (Tc)

Element 43 · transition metal · group 7, period 5

Electron shells, 2 + 8 + 18 + 13 + 2. The outer shell is highlighted - it is the only one that takes part in bonding.

Technetium is element 43, a transition metal in group 7 and period 5. Its electron configuration is [Kr] 4d5 5s2. The shells fill 2, 8, 18, 13, 2. Courses differ here. Counting only the outer s subshell gives 2; counting the inner d subshell with it gives 7, which is the group number. It commonly forms ions with a charge of +7.

43 protons
2/7 valence e−
+7
d-block

Properties

Atomic number	43
Symbol	Tc
Standard atomic weight	98 u
Group	7
Period	5
Block	d-block
Category	transition metal
Electron configuration	1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁵ 5s²
Noble-gas notation	[Kr] 4d⁵ 5s²
Electrons per shell	2, 8, 18, 13, 2
Valence electrons	2 or 7
Common ionic charge	+7
Electronegativity (Pauling)	1.9
Protons / electrons	43 / 43

Electron configuration of technetium

Orbitals fill from the lowest energy upward. Writing that out for technetium gives 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁵ 5s², which is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d5 5s2 in plain text.

Everything up to Kr is the same as in that noble gas, so it is usually abbreviated to [Kr] 4d⁵ 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	5	10
5s	2	2

Technetium ion charge

Technetium commonly forms ions with a charge of +7.

Common questions

How many valence electrons does technetium have?

There is no single agreed answer for technetium. Courses differ here. Counting only the outer s subshell gives 2; counting the inner d subshell with it gives 7, which is the group number. Check which convention your course uses before answering.

What is the electron configuration of technetium?

1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d5 5s2, or [Kr] 4d5 5s2 written from the previous noble gas. Orbitals fill lowest energy first.

What is the charge of technetium?

Technetium commonly forms ions with a charge of +7. Transition metals have several accessible oxidation states, which is why more than one charge is listed.

How many protons, electrons and neutrons does technetium have?

A neutral technetium atom has 43 protons and 43 electrons. Its standard atomic weight is 98, so the most common isotope has about 55 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 43 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.