Chemistry

Any type of bonding can result in crystalline lattices. A crystal is a highly ordered arrangement of particles. The forces holding the particles together can differ, but as long as the solid forms slowly enough, the particles can line themselves up into a lattice.

Ionic bonding can produce crystals such as copper sulfate.

Covalent bonding can produce molecular crystals such as iodine or giant covalent lattices such as diamond.

Metallic bonding can produce crystals of metals, though for practical reasons mostly we make sure the metals we use every day contain only very tiny ones.
Ionic bond is the chemical bond that makes crystalline lattices. This is taught during science.

A+...subscript.

That is the subscript in a chemical formula. For example, oxygen by itself in a jar is usually diatomic (except for ozone, but that doesn't last long in standard temperatures and pressures) so its molecular formula is O2, and so is hydrogen H2, water molecule has one oxygen bonded to two hydrogen H2O, so when we write the formula for making water it has to take into account that each molecule of oxygen forms two molecules of water which needs two molecules of hydrogen (remember the least common multiple stuff we went through in grade school?) and the energy it has to take from its immediate viscinity

O2 + 2H2 + ΔE = 2H2O

keeping in mind that most formulas don't include the unusual things, like a mole of oxygen will have a very small amount of single oxygen molecules and some ozone, but they don't last long enough to be useful, and they are usually in small enough amounts that scientists use the ever present phrase "small enough to be ignored"