Technetium (Tc)
Technetium is element 43, a transition metal in group 7, period 5. A neutral atom has 43 protons, 54 neutrons and 43 electrons, 2 of them valence electrons.
Transition metal- Atomic number
- 43
- Atomic mass
- 96.906 u
- Valence electrons
- 2*
- Protons · neutrons
- 43 · 54
- Electrons per shell
- 2, 8, 18, 13, 2
- At room temperature
- solid
Bohr model of technetium
The Bohr model draws technetium as a nucleus of 43 protons and 54 neutrons, with its 43 electrons on 5 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 13 in shell 4, 2 in shell 5. Press Build the atom to watch the shells fill from the inside out. The outer ring (the O shell) is dashed: the electrons there are the ones that take part in chemistry.
Real electrons don't travel in neat circles. They live in fuzzy orbitals, shown below, but the Bohr picture is the quickest way to count shells and valence electrons.
Electron configuration of technetium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d⁵
Short form (noble gas notation): [Kr] 5s² 4d⁵. The [Kr] stands for the electrons of krypton, the noble gas before it.
How many valence electrons does technetium have?
Technetium has 2 valence electrons.
Technetium is a transition metal, so its valence electrons are less clear-cut than for main-group elements. It has 2 electrons in its outermost shell (shell 5), and electrons in its inner d subshell can also take part in bonding.
Protons, neutrons and electrons
| Protons | 43 | equal to the atomic number |
|---|---|---|
| Electrons | 43 | equal to the protons in a neutral atom |
| Neutrons | 54 | mass number 97 − 43 protons |
Atoms of the same element can have different numbers of neutrons (isotopes). The count above uses the rounded atomic mass, the way it's taught in class.
Technetium properties
| Symbol | Tc |
|---|---|
| Category | Transition metal |
| Group · period · block | 7 · 5 · d |
| Atomic mass | 96.906 u |
| State at 25 °C | solid |
| Melting point | 2,430 K (2,160 °C, 3,910 °F) |
| Boiling point | 4,538 K (4,260 °C, 7,710 °F) |
| Density | 11 g/cm³ |
| Electronegativity (Pauling) | 1.9 |
| Atomic radius | 209 pm |
| First ionization energy | 7.28 eV |
| Electron affinity | 0.55 eV |
| Oxidation states | +7, +6, +4 |
| Common ion charge | +7, +6 |
| Discovered | 1937 by Emilio Segrè |
Where technetium sits on the periodic table
Group 7: Manganese, Rhenium, Bohrium.
Questions about technetium
How many valence electrons does technetium have?
Technetium has 2 valence electrons in its outer shell; inner d or f electrons can also bond.
How many protons, neutrons and electrons does technetium have?
A neutral technetium atom has 43 protons and 43 electrons. Its most common form has about 54 neutrons (mass number 97 − 43 protons).
What is the electron configuration of technetium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d⁵, written in short form as [Kr] 5s² 4d⁵.
What does the Bohr model of technetium look like?
A nucleus of 43 protons and 54 neutrons, circled by 5 electron shells holding 2, 8, 18, 13, 2 electrons.
What is the atomic number of technetium?
43. The atomic number is the number of protons in the nucleus, and it is what makes an atom technetium.