1. An ion is a charged atom. A molecule is a neutrally-charged combination of atoms.
2. A molecule is a combination of atoms. It can consist of atoms from one or more elements. For example, an oxygen molecule comprises two oxygen atoms. A compound is a substance made up of a combination of atoms of different elements. For example, water is a compound of hydrogen and oxygen.
3. An electron dot diagram is a simple way of representing the bond and electronic structure of molecules. A formula is a written representation of the types and numbers of atoms in a molecule.
4. As above...a formula denotes which atoms are in a molecule and how many. For example, H2SO4 tells us there are two hydrogen atoms, one sulfur atom and four oxygen atoms in each molecule of sulfuric acid.
5. An ionic bond is a type of chemical bond that stems from electrostatic attraction between ions with opposite charges. A covalent bond is another type of chemical bond that involves sharing of electrons between atoms in order to achieve a stable electronic structure for the molecule as a whole.