Scandium (Sc)
Scandium is element 21, a transition metal in group 3, period 4. A neutral atom has 21 protons, 24 neutrons and 21 electrons, 2 of them valence electrons.
Transition metal- Atomic number
- 21
- Atomic mass
- 44.956 u
- Valence electrons
- 2*
- Protons · neutrons
- 21 · 24
- Electrons per shell
- 2, 8, 9, 2
- At room temperature
- solid
Bohr model of scandium
The Bohr model draws scandium as a nucleus of 21 protons and 24 neutrons, with its 21 electrons on 4 circular shells: 2 in shell 1, 8 in shell 2, 9 in shell 3, 2 in shell 4. Press Build the atom to watch the shells fill from the inside out. The outer ring (the N 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 scandium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹
Short form (noble gas notation): [Ar] 4s² 3d¹. The [Ar] stands for the electrons of argon, the noble gas before it.
How many valence electrons does scandium have?
Scandium has 2 valence electrons.
Scandium 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 4), and electrons in its inner d subshell can also take part in bonding.
Protons, neutrons and electrons
| Protons | 21 | equal to the atomic number |
|---|---|---|
| Electrons | 21 | equal to the protons in a neutral atom |
| Neutrons | 24 | mass number 45 − 21 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.
Scandium properties
| Symbol | Sc |
|---|---|
| Category | Transition metal |
| Group · period · block | 3 · 4 · d |
| Atomic mass | 44.956 u |
| State at 25 °C | solid |
| Melting point | 1,814 K (1,540 °C, 2,810 °F) |
| Boiling point | 3,109 K (2,840 °C, 5,140 °F) |
| Density | 2.99 g/cm³ |
| Electronegativity (Pauling) | 1.36 |
| Atomic radius | 211 pm |
| First ionization energy | 6.561 eV |
| Electron affinity | 0.188 eV |
| Oxidation states | +3 |
| Common ion charge | +3 |
| Discovered | 1879 by Lars Fredrik Nilson |
Where scandium sits on the periodic table
Group 3: Yttrium.
Questions about scandium
How many valence electrons does scandium have?
Scandium has 2 valence electrons in its outer shell; inner d or f electrons can also bond.
How many protons, neutrons and electrons does scandium have?
A neutral scandium atom has 21 protons and 21 electrons. Its most common form has about 24 neutrons (mass number 45 − 21 protons).
What is the electron configuration of scandium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹, written in short form as [Ar] 4s² 3d¹.
What does the Bohr model of scandium look like?
A nucleus of 21 protons and 24 neutrons, circled by 4 electron shells holding 2, 8, 9, 2 electrons.
What is the atomic number of scandium?
21. The atomic number is the number of protons in the nucleus, and it is what makes an atom scandium.