How many hydrogen atoms are present in .46 moles of NH3

2.78 x 10²³

Explanation:

1 mole contains 6.02 x 10²³ hydrogen atoms => 0.46 mole contains 0.46(6.02 x 10²³) hydrogen atoms or 2.78 x 10²³ atoms.

Caution => When to use H vs H₂ => This problem is specific for 'hydrogen atoms' but some may simply say hydrogen. In such cases use H₂ or 'molecular hydrogen' is the focus. it's a matter of semantics, H vs H₂.    

b..

is the correct one

explanation:

covalent bonds form as valence electrons are shared between two atoms. lewis structures and structural formulas are common ways of showing the covalent bonding in organic molecules. formal charge describes the changes in the number of valence electrons as an atom becomes bonded into a molecule.

clouds form

solid ice forms on leaves.

water droplets form on grass.