Final answer:
An ion is an atom or molecule with an electric charge due to the loss or gain of electrons. A cation is a positively charged ion, like Na+, while an anion is negatively charged, such as Cl-. Polyatomic ions, like the nitrate ion NO3−, consist of multiple atoms bonded together with an overall charge.
Step-by-step explanation:
An ion is an atom or molecule that has a net electric charge due to the loss or gain of one or more electrons. When an atom loses electrons, it becomes a positively charged ion, known as a cation. A good example is the sodium ion (Na+), which is a cation with a +1 charge. This occurs because sodium loses one electron and has more protons than electrons. Conversely, when an atom gains electrons, it becomes a negatively charged ion, or an anion. Chlorine, for instance, can gain an electron to form the chloride ion (Cl−), thus acquiring a -1 charge.
Polyatomic ions are charged ions composed of two or more atoms covalently bonded or of a metal complex that can be considered to be acting as a single unit. The charge of polyatomic ions is not simply the sum of the charges on the constituent atoms, but rather, it is the result of the overall charge of the compound that the atoms form when bonding together. One example of a polyatomic ion is the nitrate ion (NO3−), which consists of one nitrogen atom and three oxygen atoms and has an overall charge of -1.