Aluminum (Al)
Aluminum is element 13, a post-transition metal in group 13, period 3. A neutral atom has 13 protons, 14 neutrons and 13 electrons, 3 of them valence electrons.
Post-transition metal- Atomic number
- 13
- Atomic mass
- 26.982 u
- Valence electrons
- 3
- Protons · neutrons
- 13 · 14
- Electrons per shell
- 2, 8, 3
- At room temperature
- solid
Bohr model of aluminum
The Bohr model draws aluminum as a nucleus of 13 protons and 14 neutrons, with its 13 electrons on 3 circular shells: 2 in shell 1, 8 in shell 2, 3 in shell 3. Press Build the atom to watch the shells fill from the inside out. The outer ring (the M 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 aluminum
1s² 2s² 2p⁶ 3s² 3p¹
Short form (noble gas notation): [Ne] 3s² 3p¹. The [Ne] stands for the electrons of neon, the noble gas before it.
How many valence electrons does aluminum have?
Aluminum has 3 valence electrons.
Aluminum 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 | 13 | equal to the atomic number |
|---|---|---|
| Electrons | 13 | equal to the protons in a neutral atom |
| Neutrons | 14 | mass number 27 − 13 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.
Aluminum properties
| Symbol | Al |
|---|---|
| Category | Post-transition metal |
| Group · period · block | 13 · 3 · p |
| Atomic mass | 26.982 u |
| State at 25 °C | solid |
| Melting point | 933.4 K (660 °C, 1,220 °F) |
| Boiling point | 2,792 K (2,520 °C, 4,570 °F) |
| Density | 2.7 g/cm³ |
| Electronegativity (Pauling) | 1.61 |
| Atomic radius | 184 pm |
| First ionization energy | 5.986 eV |
| Electron affinity | 0.441 eV |
| Oxidation states | +3 |
| Common ion charge | +3 |
| Discovered | Known since ancient times |
Where aluminum sits on the periodic table
Group 13: Boron, Gallium, Indium, Thallium, Nihonium.
Questions about aluminum
How many valence electrons does aluminum have?
Aluminum has 3 valence electrons.
How many protons, neutrons and electrons does aluminum have?
A neutral aluminum atom has 13 protons and 13 electrons. Its most common form has about 14 neutrons (mass number 27 − 13 protons).
What is the electron configuration of aluminum?
1s² 2s² 2p⁶ 3s² 3p¹, written in short form as [Ne] 3s² 3p¹.
What does the Bohr model of aluminum look like?
A nucleus of 13 protons and 14 neutrons, circled by 3 electron shells holding 2, 8, 3 electrons.
What is the atomic number of aluminum?
13. The atomic number is the number of protons in the nucleus, and it is what makes an atom aluminum.