periodic table with charges and polyatomic ions

Thus, the compound will be electrically neutral, with the same number of positive and negative charges. Two aluminum ions, each with a charge of 3+, would give us six positive charges, and three oxide ions, each with a charge of 2−, would give us six negative charges. The formula of an ionic compound must have a ratio of ions such that the numbers of positive and negative charges are equal.įor example, if a compound contains aluminum and oxygen in the form of Al 3+ and O 2−, the formula of the compound would be Al 2O 3. Thus, ionic compounds are electrically neutral, even though they contain positive and negative ions. In every ionic compound, the total number of positive charges of the cations equals the total number of negative charges of the anions. For example, copper can form ions with a 1+ or 2+ charge, and iron can form ions with a 2+ or 3+ charge. Transition metals and some other metals often exhibit variable charges that are not predictable by their location in the table. The name of the anions is the name of the nonmetallic element with its ending replaced by the suffix -ide, so O 2− is called oxide. The anion, O 2−, has the same number of electrons as the next noble gas – neon. This results in an anion with 8 protons, 10 electrons, and a 2− charge, and is symbolized as O 2−. For example, a neutral oxygen atom, with 8 protons and 8 electrons, readily gains two electrons. That is, atoms of group 17 gain one electron and form anions with a 1− charge atoms of group 16 gain two electrons and form ions with a 2− charge, and so on. Moving from the far right to the left on the periodic table, nonmetal elements often gain electrons to form anions with the same number of electrons as an atom of the next noble gas in the periodic table, and a negative charge equal to the number of groups moved left from the noble gases. The compound formed by this transfer is stabilized by the electrostatic attractions (ionic bonds) between the oppositely charged ions. The number of water molecules is indicated using Greek-numeral-prefixes followed by the suffix ‘–hydrate.’ The chemical name of CaCl 2∙2H 2O is calcium chloride dihydrate.Īn element composed of atoms that readily lose electrons (a metal) can react with an element composed of atoms that readily gain electrons (a nonmetal) to produce ions through complete electron transfer. Hydrated ionic compounds or hydrates like CaCl 2∙2H 2O contain chemically-associated water molecules. Therefore the ionic compounds are sodium perbromate, sodium bromate, sodium bromite, and sodium hypobromite. Lastly, the oxyanion with one oxygen atom fewer than the oxyanion ending with ‘–ite’ obtains the prefix ‘hypo–’. The suffix changes to ‘–ite’ with one less oxygen, or it is given the prefix ‘per–’ with one oxygen atom more. The most common oxyanion of an element is named by combining the element’s base-name with the suffix ‘–ate’. Polyatomic anions containing oxygen, or oxyanions, are named based on the number of oxygen atoms.įor example, multiple polyatomic ionic compounds are formed between sodium and oxyanions of bromine. Polyatomic ionic compounds follow the same nomenclature rules, but apply the polyatomic anion name instead of the suffix ‘-ide’. Thus, the names are sodium iodide, iron(II) bromide, and iron(III) bromide. Iron forms two types of cations, which are displayed using parenthesized Roman-numerals. Since sodium forms only a single type of cation, the parenthesized Roman-numeral is excluded. The anion base-name ending with the suffix ‘–ide’ follows last.Ĭonsider the following three molecules. The chemical formula helps determine the name of the compound.īinary ionic compounds name the metal cation first, succeeded by a parenthesized Roman-numeral indicating the metal charge if the metal can exist in different cationic states. The cationic subscript is numerically matched to the anionic charge and vice versa, generating a charge-neutral chemical formula.Īll ionic compounds are named by following a systematic naming convention called the chemical nomenclature. Next, the overall charge within the formula is balanced by employing a crisscross method. Conversely, fluorine from group 17 forms anions with an ionic-charge of 1−. Calcium from group 2 forms cations with an ionic-charge of 2+. Ionic charges can be determined from the group number of the element in the periodic table. Start with the cations followed by anions. First, specify the ions of each element and their respective ionic charges. These compounds are represented by chemical formulas.Ĭonsider calcium fluoride. Ionic compounds form ionic bonds between positively charged metal ions, or cations, and negatively charged nonmetal ions, or anions.

Periodic table with charges and polyatomic ions