How do you determine valence electrons of a metal? A non Metal?

Check the electronic configuration of elements.

Explanation:

▪Valence electrons are the elwctrons present in the outermost shell of any element.

For example,

Electronic Configuration of Sodium = 2,8,1

Here , Sodium has 1 valence electrons.

▪Valency of an element is the total no. of electrons to be gained/losed in order to achieve duplet/octate state.

For example,

Electronic configuration of Sodium = 2,8,1

Sodium can achieve octate state either by losing 1 electron or gaining 7 electrons. But losing 1 electron is eay than gaining 7 electrons. So Valency of Sodium = +1

☆Metals have 1 or 2 or 3 valence electrons.

☆Non metals have 4 or 5 or 6 or 7 valence electrons.

☆Noble gases tend to stay in duplet/octate state i.e they have 2 or 8 valence electrons.

it's all four options.