Question

How does an atom's valence electron configuration determine its place in the periodic table?

Answer 1

Elements in a family (groups, the vertical bits) have the same number of valence electrons. The level of energy of an atom's valence electron(s) determines its period, (the horizontal lines).

Explanation:

When you're looking for the element, try to fill in from what you're given.

E.g: Let's say you're working with Aluminium(Al),

That configuration is `1s^2` `2s^2` `2p^6` `3s^2` `3p^1`

See how it filling in across until it reached Aluminium?

Now, if you had `1s^2` `2s^2` `2p^6` `3s^2` `3p^6` `4s^2` `3d^7` it would be the same thing, fill in until you reach your desired place.

You would get Co, Cobalt.

Hope this helps.