Explain why the symbol for an atom of the element oxygen and the formula for a molecule of oxygen differ.

See below.

Explanation:

In the scientific setting, a few elements exist in monoatomic state, meaning their atoms could persist as single isolated atoms. The symbol for oxygen's atom is O which actually is the symbol for monoatomic oxygen.

In order to gain a stable electronic configuration, two oxygen atoms share electrons with each other to form covalent bonds. Hence, we get a entity which consists of 2 oxygen atoms with a covalent bond which is O2, molecule of oxygen.

nacl or sodium chloride is an ionic compound. this is because an ionic compound pertains to a compound that consists of positively and negatively charged ions. in this case, na (sodium) has a tendency to lose one electron when it reacts with with other atoms, so the resulting sodium ion contains 11 protons and 10 electrons, thus making it positively charged (na+), when chlorine reacts, it usually gains one electron to form an ion called chloride, thus making it negatively charged ( since the ions are oppositely charged, they attract.