In what way are elements in the same column of the periodic table the same

1) they have similar chemical properties.

for example fluorine from the 17th column is a non metal so does all the elements of that group.

2) they have same valence electrons in their outermost shell

example

electronic configuration of

hydrogen 1, lithium 2,1, sodium 2,8,1 and so on.

3) have same valency.