In , the nitrogen is bound covalently to the three oxygens, and the complex has an overall of .

Sodium has a charge of , and is ionically bound to the  complex.

When put into water, the compound will dissociate into  and .

HCl is an ionic compound, while the other answer choices have only covalent bonds.

The octet rule requires that each atom in the molecule has eight valence electrons, fully filling the s and p subshells. Atoms that have a full octet tend to be more stable and lower in energy.

In the compound , each fluorine has seven initial valence electrons and boron has three initial valence electrons. Upon forming the compound bonds, boron shares its three electrons with each fluorine through covalent bonds. This givens each fluorine a full octet, but leave boron with only three covalent bonds, resulting in only six valence electrons. Boron does not satisfy the octet rule in this compound.

Each atom in the other listed compounds forms bonds to generate a full octet. Sodium chloride achieves this through an ionic bond. Methanal and diatomic oxygen both use double bonds to help achieve octets.

The empirical formula of a compound is the simplest whole number ratio of the elements in the compound, whereas the molecular formula gives the exact number of atoms of each element in the compound—this is usually a multiple of the empirical formula. If the empirical formula of a compound is CH, a common molecular formula is C₆H₆ (benzene).

Cobalt (II) is Cobalt in its second oxidation state, , and the chemical formula for Nitrate is . The neutral salt is .

Ferrous is the name for Iron (II), or . Sulfide is the anion of sulfur, . The chemical formula for ferrous sulfide is .

Remember that sodium wants to lose only one electron in order to achieve a stable octet. Meanwhile, oxygen needs to gain 2 electrons in order to achieve a stable octet. As a result, the expected compound involves two sodium atoms, each giving up one electron in order to fill oxygen's octet.

We should first remember the difference between sulfate, sulfite, and sulfide. Sulfate is , sulfite is ` and sulfide is .

The only answer choices that could be right must have  in them. We then need to see that barium usually has a charge of , as the periodic table shows us, and so we need a charge of  to cancel that out. The answer is .

is a saturated hydrocarbon with an organic functional group, , or alcohol.

is propane, so we will remove the "e" from the end of that name and add the suffix "ol" to denotate an alcohol, so the correct answer is propanol.

Propenol is propanol with a double bond in the hydrocarbon chain. Ethanol is a saturated two-carbon chain with an alcohol functional group.

Covalent non-metal/non-metal compounds are named by taking the name of each element and appending the apropriate greek prefix to indicate the number of each atom present—in this case, di- for two and tetra- for four. The end of the more electronegative element is substituted with "ide". This gives the name of dinitrogen tetraoxide.

Ionic compounds are named by naming the cation followed by the anion. Since the cation, cesium, is an alkali metal the oxidation state, should not be specified. Alkali metals will always have an oxidation state of 1. The anion, , is sulfate. Together, the full name of the compound is cesium sulfate.