What best explains the formula unit for a compound made from fluorine and hydrogen?

Question

HF, because fluorine is short of one electron, and hydrogen is in excess of one electron.
HF, because both fluorine and hydrogen are capable of forming only one covalent bond.
H2F, because fluorine is short of two electrons, and hydrogen is short of one electron.
H2F, because fluorine is capable of forming one, and hydrogen is capable of forming two covalent bonds.

Answer 1

The best explanation for the formula unit for a compound made from fluorine and hydrogen is:

HF, because both fluorine and hydrogen are capable of forming only one covalent bond.

In this context, hydrogen can form only one bond because it has one electron and needs one more to achieve a full valence shell (the duet rule). Fluorine has seven valence electrons and needs one more to complete its octet, so it also forms one bond. Therefore, the correct molecular formula for the compound formed between hydrogen and fluorine is HF.