Define coordination number and chemical bond. State the coordination number of the cation in NaCl and CsCl.

Here are the answers to the questions:

i) The coordination number of an ion in a crystal structure is the number of oppositely charged ions that immediately surround a given ion in the lattice.

ii) State the coordination number of the cation in:
A) $\text{NaCl}$: The coordination number of the $\text{Na}^+$ cation is 6.
B) $\text{CsCl}$: The coordination number of the $\text{Cs}^+$ cation is 8.

i) A chemical bond is a lasting attraction between atoms, ions, or molecules that enables the formation of chemical compounds. It results from the electrostatic forces of attraction between opposite charges (e.g., in ionic bonds) or the sharing of electrons (e.g., in covalent bonds).