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

Nov 28, 2016

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 $1 {s}^{2}$$2 {s}^{2}$$2 {p}^{6}$$3 {s}^{2}$$3 {p}^{1}$

See how it filling in across until it reached Aluminium?

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

You would get Co, Cobalt.

Hope this helps.