In which grouping of the periodic table do the elements have similar properties?

only columns

both rows and columns

only rows
in the periods

only columns

Explanation:

All atoms of elements present in same group or column having same number of valance electrons. Thus the elements in same group having same properties.

For example:

Consider the second group. It consist of alkaline earth metals. There are six elements in second group. Beryllium, magnesium, calcium, strontium, barium and radium.

All have two valance electrons.

Electronic configuration of Beryllium:

Be = [He] 2s²

Electronic configuration of magnesium.

Mg = [Ne] 3s²

Electronic configuration of calcium.

Ca = [Ar] 4s²

Electronic configuration of strontium.

Sr = [Kr] 5s²

Electronic configuration of barium.

Ba = [Xe] 6s²

Electronic configuration of radium.

Ra = [ Rn] 7s²

They are present in group two and have same number of valance electrons (two valance electrons) and show similar reactivity.

They react with oxygen and form oxide.

2Ba   +   O₂   →    2BaO

2Mg  +   O₂   →    2MgO

2Ca +   O₂   →    2CaO

this oxide form hydroxide when react with water,

BaO  + H₂O   →  Ba(OH)₂

MgO  + H₂O   →  Mg(OH)₂

CaO  + H₂O   →  Ca(OH)₂

With sulfur,

Mg + S   →  MgS

Ca + S   →  CaS

Ba + S   →  BaS

the answer is na (sodium)