Gallium (Ga)
Gallium is element 31, a post-transition metal in group 13, period 4. A neutral atom has 31 protons, 39 neutrons and 31 electrons, 3 of them valence electrons.
Post-transition metal- Atomic number
- 31
- Atomic mass
- 69.723 u
- Valence electrons
- 3
- Protons · neutrons
- 31 · 39
- Electrons per shell
- 2, 8, 18, 3
- At room temperature
- solid
Bohr model of gallium
The Bohr model draws gallium as a nucleus of 31 protons and 39 neutrons, with its 31 electrons on 4 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 3 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 gallium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p¹
Short form (noble gas notation): [Ar] 4s² 3d¹⁰ 4p¹. The [Ar] stands for the electrons of argon, the noble gas before it.
How many valence electrons does gallium have?
Gallium has 3 valence electrons.
Gallium is in group 13, and for groups 13–18 you subtract 10 from the group number: 13 − 10 = 3. It tends to lose them and form a +3 ion.
Protons, neutrons and electrons
| Protons | 31 | equal to the atomic number |
|---|---|---|
| Electrons | 31 | equal to the protons in a neutral atom |
| Neutrons | 39 | mass number 70 − 31 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.
Gallium properties
| Symbol | Ga |
|---|---|
| Category | Post-transition metal |
| Group · period · block | 13 · 4 · p |
| Atomic mass | 69.723 u |
| State at 25 °C | solid |
| Melting point | 302.9 K (29.8 °C, 85.6 °F) |
| Boiling point | 2,477 K (2,200 °C, 4,000 °F) |
| Density | 5.91 g/cm³ |
| Electronegativity (Pauling) | 1.81 |
| Atomic radius | 187 pm |
| First ionization energy | 5.999 eV |
| Electron affinity | 0.3 eV |
| Oxidation states | +3 |
| Common ion charge | +3 |
| Discovered | 1875 by Lecoq de Boisbaudran |
Where gallium sits on the periodic table
Group 13: Boron, Aluminum, Indium, Thallium, Nihonium.
Questions about gallium
How many valence electrons does gallium have?
Gallium has 3 valence electrons.
How many protons, neutrons and electrons does gallium have?
A neutral gallium atom has 31 protons and 31 electrons. Its most common form has about 39 neutrons (mass number 70 − 31 protons).
What is the electron configuration of gallium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p¹, written in short form as [Ar] 4s² 3d¹⁰ 4p¹.
What does the Bohr model of gallium look like?
A nucleus of 31 protons and 39 neutrons, circled by 4 electron shells holding 2, 8, 18, 3 electrons.
What is the atomic number of gallium?
31. The atomic number is the number of protons in the nucleus, and it is what makes an atom gallium.