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Ionic bonding is a type of chemical bond formed through the electrostatic attraction between oppositely charged ions. When a metal, like sodium (Na), meets a nonmetal, such as iodine (I), it forms an ionic compound.
In this process, the metal loses electrons to become a positively charged cation, while the nonmetal gains electrons to become a negatively charged anion. For example, in NaI, sodium donates an electron to iodine, resulting in the formation of Na鈦� and I鈦� ions.
Ionic compounds generally have high melting and boiling points due to the strong interactions between the ions in a lattice structure.
They often dissolve in water and conduct electricity when in molten or dissolved form.

Covalent bonding occurs when two nonmetals share pairs of electrons to achieve full outer electron shells.
In the example of \(\mathrm{PF}_5\), phosphorus (P) and fluorine (F) are both nonmetals and engage in covalent bonding.
This allows them to form a stable molecular compound by sharing electrons rather than transferring them completely. \(\mathrm{SCl}_2\) and \(\mathrm{N}_2\mathrm{O}_4\) are other examples of molecular compounds created through covalent bonds.
Covalent compounds generally have lower melting and boiling points compared to ionic compounds. They are often gases or liquids at room temperature.

Understanding how metals and nonmetals interact helps in identifying whether compounds are ionic or molecular.
Typically, when a metal reacts with a nonmetal, the tendency is to form an ionic compound due to electron transfer. Metals like calcium (Ca) and lanthanum (La) lose electrons, while nonmetals like chlorine (Cl) or phosphorus (P) gain electrons to form ionic bonds.
This results in compounds like \(\mathrm{Ca}(\mathrm{NO}_3)_2\) and \(\mathrm{LaP}\), where electrostatic forces hold the compounds together.
Examination of the elements involved provides insight into the bonding nature and helps predict compound types.

Polyatomic ions are charged entities composed of two or more atoms covalently bonded together. They act as a single unit with a net charge, playing a significant role in ionic compounds.
For example, nitrate (\(\mathrm{NO}_3^{-}\)) and carbonate (\(\mathrm{CO}_3^{2-}\)) are common polyatomic ions.
These ions can combine with metals like calcium in \(\mathrm{Ca}(\mathrm{NO}_3)_2\) or cobalt as in \(\mathrm{CoCO}_3\), resulting in ionic compounds. These compounds exhibit properties typical of ionic substances, such as high melting points and electrical conductivity in aqueous or molten states.
Recognizing polyatomic ions is essential for understanding the composition and behavior of various compounds.