Question

1. why does he have a smaller atomic radius than h?

h has more hydrogen bonding
he has 2 positively charged protons in the nucleus pulling the negatively charged electrons closer.
he is in the second period
all of these

1. which of the following atoms is a halogen?

h
he
c
f

Explanation:

For question 3, atomic radius is related to the effective nuclear charge. Helium has 2 protons in its nucleus which pull electrons closer compared to hydrogen with 1 proton. Hydrogen - bonding is not relevant to atomic radius comparison here and helium is in the first period. For question 4, halogens are elements in group 17 of the periodic table. Fluorine (F) is a halogen while hydrogen (H), helium (He) and carbon (C) are not.

Answer:

1. He has 2 positively charged protons in the nucleus pulling the negatively charged electrons closer.
2. F