How can I draw an orbital diagram for chloride ion?

To write electron configurations in orbital notation, find the element on the periodic table. In this case, the particle (`Cl^-1`) is an anion with a charge of -1, so we also need to move forward by one atomic number, meaning that `Cl^-1` has the same electron configuration as `Ar`.

Electron orbitals are regions around a nucleus that can hold a maximum of two electrons. When filled, the first electron orbital can be represented as `1s_2`. The `1` represents the energy level of the orbital, the `s` represents that it contains electrons from the first two groups of the periodic table, and the `2` represents the number of electrons in the orbital. The first number increases as you move down periods on the periodic table and the letter changes as you move from block to block on the periodic table.

Following these rules, we can write the electron orbital notation of `Cl^-1` as:

`1s_2 2s_2 2p_6 3s_2 3p_6`

To draw this as a diagram, draw a circle representing an orbital for every two electrons, and fill them up one by one with lines representing electrons.

X X XXX X XXX

Note that you cannot add a second line to an orbital until all the other orbitals in the same letter block (`s, p, d,`etc.) have one line