Ammonium is NH₄₊. It is formed by the association of NH₃ with H+. Thus, NH3 acts as a Lewis base, and H+ is a Lewis acid. This is a coordinate covalent bond, and there is one of these in the molecule. The remaning three bonds are polar covalent (N–H bonds).

Covalent compounds generally form between two nonmetals that will both share electrons to complete their octets. Boron (B) is a metalloid and can act as a metal or nonmetal. In its bonds with fluorine (F), however, the two compounds have relatively similar electronegativities. A lack of difference in electronegativity results in covalent bonds.

Ionic compounds form between metals and nonmetals through a transfer of electrons, Metallic compounds are built from only metals. Polyatomic ions will have a formal charge.

Polarity in a bond results from an uneven sharing of electrons. An extreme example is an ionic bond, in which an electron is almost fully transferred from one atom to another due to the second atom's electron affinity.

In order to generate an uneven pull on shared electrons, the atoms involved in the bond must have significantly differing electronegativities. This will cause one atom to pull electrons closer to its nucleus, away from the other atom involved.

Molecular and electronic geometry can affect the polarity of a compound, but do not directly affect polarity of a single given bond. Atomic radius does not play a significant role in polarity.

In carbon has a single bond to each hydrogen and a double bond to oxygen. Carbon must form four bonds to satisfy the octet rule. Only single bonds can be formed with hydrogen, but oxygen can form double bonds. The carbon will thus form two single bonds and one double bond.

The definition of a coordinate covalent bond is that one of the atoms donates both of the electrons being shared. This corresponds with the correct answer choice.

Carbon dioxide has a double bond between the carbon and oxygen molecules. Since there is a moderately large electronegativitiy difference between C and O, the bond can be described as polar covalent.

Though the bonds themselves are polar, the overall symmetry of the molecule means that carbon dioxide has a net zero dipole and is a nonpolar compound.

In a covalent bond, electrons are shared between two nonmetals. If there is a metal in the compound, that is called an ionic compound, not a covalent compound. Ionic bonds involve the complete transfer of an electron from one species to another.

An ionic bond is a bond between a metal (Rb) and a nonmetal(Cl)

Ionic compounds are formed between metals, which want to loose electrons, and nonmetals, which want to gain electrons. The sodium (Na) will completely transfer an electron to the chlorine (Cl), giving both atoms a complete octet without sharing electrons.

Covalent compounds generally form between two nonmetals that will both share electrons to complete their octets. Metallic compounds are built from only metals. Polyatomic ions will have a formal charge.

Covalent bonds are formed when two nonmetals are bonded together. This covalent bond means that the electrons are shared by the two atoms in order to satisfy each atom's octet. There is very little difference in the electronegativities of the two atoms involved in the bond, so neither atom pulls the electrons closer to its nucleus.

Ionic bonds are formed between a metal and a nonmetal. Due to the dramatic difference between the electronegativities of metals and nonmetals, the electrons are pulled tightly to the nonmetal, and away from the metal nucleus. This results in each atom having a full octet, even though the electrons are not shared.

Carbon and oxygen are both nonmetals, so we would expect only covalent bonds in carbon dioxide.