What is common to all contact forces

Friction is common to all contact forces

The answers are very vague but basically the nonmetal group would be anything but the middle —

So the nonmetals would be the first , second group and then the last group, second to last group, all the way until you see B for Boron. Anything in the middle of the periodic table is a metal. So I would say along the top but to note, there are particular elements in group that aren’t along the top of the periodic table that would be considered a nonmetal!

I hope this helps you and if you are still confused let me know! :)