Atomic radius- a measure of the size of its atoms, usually the mean or typical distance from the center of the nucleus to the boundary of the surrounding cloud of electrons. Electron Affinity-the electron affinityof an atom or molecule is defined as the amount of energy released or spent when an electron is added to a neutral atom or molecule in the gaseous state to form a negative ion. Electronegativity-a measure of the tendency of an atom to attract a bonding pair of electrons. The Pauling scale is the most commonly used. Fluorine (the most electronegative element) is assigned a value of 4.0, and values range down to caesium and francium which are the least electronegative at 0.7. Lonization energy- qualitatively defined as the amount of energy required to remove the most loosely bound electron, the valence electron, of an isolated gaseous atom to form a cation.
The type of bonds present in the compound. and the type of structure it has and the elements that are presents and the number of moles of each element in one mole of the compound.
Remark The short Answer is 6. That's why the ion has a charge of minus 2. Oxygen is doing it's best to have its outer ring have 8 electrons which is the number of outer electrons contained in the outer ring of the Noble Gas Neon.
