Arsenic (As)
Element 33 · metalloid · group 15, period 4
Arsenic is element 33, a metalloid in group 15 and period 4. Its electron configuration is [Ar] 3d10 4s2 4p3. That leaves 5 valence electrons in the outer shell, with the shells filling 2, 8, 18, 5. It is 3 electrons short of a full octet, so it gains them and carries a charge of -3, +3, +5.
- 33 protons
- 5 valence e−
- -3, +3, +5
- p-block
Arsenic Lewis dot structure
Arsenic has 5 valence electrons, so its Lewis symbol carries 5 dots: one pair and three single dots. The dots go one to a side before any of them pair up, so the unpaired ones show exactly how many bonds the atom tends to form.
Draw it in the Lewis structure generator →
Properties
| Atomic number | 33 |
|---|---|
| Symbol | As |
| Standard atomic weight | 74.922 u |
| Group | 15 |
| Period | 4 |
| Block | p-block |
| Category | metalloid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p3 |
| Noble-gas notation | [Ar] 3d10 4s2 4p3 |
| Electrons per shell | 2, 8, 18, 5 |
| Valence electrons | 5 |
| Common ionic charge | -3, +3, +5 |
| Electronegativity (Pauling) | 2.18 |
| Protons / electrons | 33 / 33 |
Electron configuration of arsenic
Orbitals fill from the lowest energy upward. Writing that out for arsenic gives 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p3, which is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p3 in plain text.
Everything up to Ar is the same as in that noble gas, so it is usually abbreviated to [Ar] 3d10 4s2 4p3. The part outside the bracket is what does the chemistry.
| Subshell | Electrons | Capacity |
|---|---|---|
| 1s | 2 | 2 |
| 2s | 2 | 2 |
| 2p | 6 | 6 |
| 3s | 2 | 2 |
| 3p | 6 | 6 |
| 3d | 10 | 10 |
| 4s | 2 | 2 |
| 4p | 3 | 6 |
Arsenic ion charge
Arsenic commonly forms ions with a charge of -3, +3, +5.
It has 5 valence electrons, so it is 3 short of a full octet and 5 above an empty outer shell. An atom takes whichever route is shorter, which is why the charge comes out as it does.
Common questions
What is the Lewis dot structure of arsenic?
The symbol As with 5 dots, one for each valence electron: one pair and three single dots. Dots go one to a side before any pair up, the same way electrons fill separate orbitals before sharing one.
How many valence electrons does arsenic have?
Arsenic has 5 valence electrons. For a main-group element the count is the group number minus 10, and arsenic is in group 15.
What is the electron configuration of arsenic?
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p3, or [Ar] 3d10 4s2 4p3 written from the previous noble gas. Orbitals fill lowest energy first.
What is the charge of arsenic?
Arsenic commonly forms ions with a charge of -3, +3, +5. With 5 valence electrons it is 3 short of an octet and 5 above an empty shell, so it takes whichever route is shorter.
How many protons, electrons and neutrons does arsenic have?
A neutral arsenic atom has 33 protons and 33 electrons. Its standard atomic weight is 74.922, so the most common isotope has about 42 neutrons.
Arsenic in Lewis structures
What the configuration above means in practice. Arsenic brings 5 valence electrons to it, and the working there starts by counting exactly that.
Nearby elements
See the ionic charge of every element →