Element 43 · Technetium (Tc)

Technetium Bohr model: diagram and electrons per shell

The technetium Bohr model shows a technetium atom (Tc) as a small nucleus with its electrons circling it in 5 shells: 2 in shell K, 8 in shell L, 18 in shell M, 13 in shell N and 2 in shell O. This page has a rotating 3D technetium Bohr model, a flat diagram, a table of the electrons in each shell and the steps to draw it yourself.

Rotate the technetium Bohr model in 3D

Drag to orbit, scroll to zoom.

This is a Bohr model of technetium (Tc), a simplified picture of a single technetium atom. Its nucleus holds 43 protons, and a neutral technetium atom has 43 electrons, arranged around it in 5 shells (2 in shell K, 8 in shell L, 18 in shell M, 13 in shell N and 2 in shell O).

Tc K · 21s² L · 82s² 2p⁶ M · 183s² 3p⁶ 3d¹⁰ N · 134s² 4p⁶ 4d⁵ O · 25s²

Technetium Bohr model diagram

Bohr model diagram of technetium: a nucleus of 43 protons with 43 electrons on 5 shells, 2 in shell K, 8 in shell L, 18 in shell M, 13 in shell N and 2 in shell O, each ring labelled with its shell letter. — The technetium Bohr model drawn flat: each ring is a shell, labelled with its letter, and every dot is an electron (2 in shell K, 8 in shell L, 18 in shell M, 13 in shell N and 2 in shell O).

Technetium electrons per shell

A neutral technetium atom has 43 electrons, one for each of its 43 protons. They fill the shells from the nucleus outwards: 2 in shell K, 8 in shell L, 18 in shell M, 13 in shell N and 2 in shell O.

Electrons in each shell of the technetium Bohr model
Shell	Shell number (n)	Electrons	Most it can hold (2n²)	Subshells
K	1	2	2	1s²
L	2	8	8	2s² 2p⁶
M	3	18	18	3s² 3p⁶ 3d¹⁰
N	4	13	32	4s² 4p⁶ 4d⁵
O	5	2	50	5s²

How the technetium Bohr model builds up, shell by shell

Watch the technetium Bohr model come together: the nucleus first, then each shell in turn, from the innermost outwards, with its electrons joining the ring. The legend names every shell and counts its electrons, so you can read off the arrangement (2 in shell K, 8 in shell L, 18 in shell M, 13 in shell N and 2 in shell O) as it forms.

Animation of the technetium Bohr model being built: a nucleus of 43 protons appears first, then each shell grows in around it and takes its electrons, giving 43 electrons on 5 shells (2 in shell K, 8 in shell L, 18 in shell M, 13 in shell N and 2 in shell O). — The technetium Bohr model built up in six seconds: the nucleus first, then each shell with its electrons, ending with 2 in shell K, 8 in shell L, 18 in shell M, 13 in shell N and 2 in shell O. Protons are red, neutrons yellow and electrons blue.

How to draw the technetium Bohr model

Find the atomic number. Technetium has atomic number 43, so a neutral atom has 43 protons and 43 electrons.
Draw the nucleus. Put a circle in the centre and write Tc in it. The 43 protons sit there with the neutrons.
Draw the shells. Sketch 5 shells as rings around the nucleus. A shell holds at most 2n² electrons: 2 in the first, 8 in the second, 18 in the third and 32 in the fourth.
Place the electrons. Fill from the inside out: 2 in shell K, 8 in shell L, 18 in shell M, 13 in shell N and 2 in shell O.
Check the total. 2 + 8 + 18 + 13 + 2 = 43, the atomic number, so every electron is accounted for.

Atomic data for the technetium Bohr model

The numbers behind the technetium Bohr model, grouped by topic. Radii are in picometres (pm) and energies in kilojoules per mole (kJ/mol).

Identity

Symbol: Tc
Atomic number: 43
Atomic mass: [98] u
Family: Transition Metals
Position: group 7, period 5
Block: d-block

Electron configuration

Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d⁵
Shorthand: [Kr] 4d⁵ 5s²
Electrons per shell: 2, 8, 18, 13, 2
Outer-shell electrons: 2 in shell O

Ionisation energies

I₁: 702
I₂: 1470
I₃: 2850

Energy to remove each electron in turn (kJ/mol). A sharp jump means the next electron comes from an inner shell.

Atomic radii

Calculated (pm): 183
Empirical (pm): 135
Covalent (pm): 128

Electronegativity and electron affinity

Electronegativity (Pauling): 1.9
Electron affinity (kJ/mol): 53

Oxidation states

+4 +7

Charges the element commonly takes in compounds.

Physical properties, abundance and history of technetium

Bulk properties of technetium, how common it is, who discovered it and some of its compounds.

Physical properties

Phase at room conditions: Solid
Appearance: Shiny gray metal
Melting point: 2156.85°C (2430 K)
Boiling point: 4264.85°C (4538 K)
Density: 11 g/cm³
Thermal conductivity (W/m·K): 50.6
Molar heat capacity (J/mol·K): 24.27
Heat of fusion (kJ/mol): 23.8
Heat of vaporisation (kJ/mol): 585

Discovery

Discovered by: Emilio Segrè
Year: 1937

Common compounds

Diaqua((P,P'-methylenebis(phosphonato-kappaO))(4-))technetium-99Tc CH6O8P2Tc
Technetium Tc-99m Oxidronate Kit CH6O7P2Tc
Technetium Tc
Technetium Tc-99m Mebrofenin C30H34Br2N4O10Tc
Technetium Tc-99m arcitumomab Tc
Technetium Tc-99m exametazime C13H25N4O3Tc
Technetium Tc-99m succimer C8H12O9S4Tc+3
technetium (99mTc) etarfolatide C29H31N11O12STc

Compounds listed in the PubChem database.

Main isotopes of technetium

Isotopes of technetium share the same 43 protons but differ in neutrons. Natural isotopes come first, then the longest-lived others.

Main isotopes of technetium: mass number, abundance, half-life and decay
Mass number	Natural abundance	Half-life	Decay
94	–	293 min	β⁺
95	–	19.258 h	β⁺
96	–	4.28 d	β⁺
97	–	4.21 My	EC
98	–	4.2 My	β⁻, β⁺
99	–	211.1 ky	β⁻

α = alpha decay, β⁻ = beta-minus, β⁺ = beta-plus, EC = electron capture, SF = spontaneous fission, p / n = proton / neutron emission.

More about technetium

Technetium on the periodic table – properties, isotopes, uses and the full technetium page.
Transition Metals – all transition metal elements and their trends.
Bohr model of every element – the Bohr model of all 118 elements.