1. Sabrina was asked by a classmate why she would place hydrogen in the first column of the periodic tab le. Which of the following reasons could she give as a response?
1. Hydrogen combines with chlorine in the same atomic ratio as sodium.
II. Hydrogen is a gas at room temperature.
III. Hydrogen forms diatomic molecules.
А A
I and II
B. Oll and III
COI only
D. Ill only

The correct option is;

C. I only

Explanation:

Given that in a chemical reaction, the number of valence electrons in the outermost shell of an atom determines the ratio in which the atom combines with other atoms to have the stable 8 (octet) valence electrons in their outermost shell, we have that atoms in a group combines with atoms in other groups, where possible, in the same ratio.

Therefore, sodium, which is in the first column (group I) combines with atoms of elements in other groups, in the same ratio as atoms of the other elements of the column 1

Since hydrogen combines with chlorine in the same ratio as sodium which is from the first column, hydrogen is also an element from the first column.