One mole of carbon atoms has a mass of exactly 12 g. Because magnesium atoms each have twice the mass of carbon atoms (24Mg compared with 12C), one mole of magnesium has a mass of 24 g. In fact, one mole of any element has a mass in grams that is equal to its relative atomic mass. One mole of iron has a mass of 56 g
An atom becomes an Ion (a) if it gains one or more electron(s) or (b) if it loses one or more electron(s). When it gains electrons it becomes negatively charged and is called an anion. When it loses electron(s) it becomes positively charged and is called a cation.