A chart of valency

Valency comes from the outer electrons. You will count the outer electrons of the elements from lithium to argon, turn them into valencies, and find the elements with the highest valency. Then the program draws the chart.

The idea. Outer electrons $1$ to $4$: the valency is that number. $5$ to $7$: it is $8$ minus that number. $8$: it is $0$.

Your tasks.

1. In outer, return the outer electrons for an atomic number from $3$ to $18$.
2. In valency, return the valency.
3. Fill top with the symbols that have the highest valency.