One example is hydrogen, which may gain (H -) or lose (H +) an electron, forming hydride compounds such as ZnH 2 (where it is an anion) and hydron compounds such as H 2O (where it is a cation).Įlements in group 18 of the periodic table – the “noble gases”, tend not to form ions due to the arrangement of their electrons which makes them generally unreactive. However, some elements are capable of forming both cations and anions given the right conditions. iron, silver, nickel), whilst most other nonmetals typically form anions (e.g. Halogens always form anions, alkali metals and alkaline earth metals always form cations. It can be possible to predict whether an atom will form a cation or an anion based on its position on the periodic table. Examples include calcium chloride (CaCl 2), potassium iodide (KI) and magnesium oxide (MgO). These oppositely charged ions then attract one other to form ionic bonds and produce ionic compounds with no overall net charge. Therefore, when atoms from a metallic and a nonmetallic element combine, the nonmetallic atoms tend to draw one or more electrons away from the metallic atoms to form ions. Conversely, most nonmetallic atoms attract electrons more strongly than metallic atoms, and so gain electrons to form anions. Consequently, they tend to lose electrons and form cations. Metallic atoms hold some of their electrons relatively loosely. Sodium (Na +), Iron (Fe 2+), Ammonium (NH 4 +)Ĭhloride (Cl -), Bromide (Br -), Sulfate (SO 4 2-) In this animated video tutorial, you will learn about ions and charges, how to assign charges to monoatomic and polyatomic ions, and the difference between ionic compounds and molecular compounds.The main differences between cations and anions are summarized in the table below. Video tutorial – Ions, Polyatomic Ions, and Ionic Compounds You can read about naming ionic compounds, and naming covalent compounds. Learning how to properly name compounds like these is important. BeBr 2 – (berylliuim bromide) cation: Be 2+, anion: Br –.K 2S – (potassium sulfide) cation: K +, anion: S 2.Mg(OH) 2 – (magnesium hydroxide) cation: Mg 2+, anion: OH –.LiF – (lithium fluoride) cation: Li +, anion: F –.NaCl – (sodium chloride) cation: Na +, anion: Cl –.For example, in NaBr, sodium is the cation, while bromine is the anion. When writing the chemical formula of a compound, cation always comes before anion. Most metals (e.g., iron, lead, gold) form cations, whereas most nonmetals (e.g., oxygen, nitrogen, sulfur) form anions. In contrast, Group 17A, which consists of halogens, always forms anions. Group 1A and 2A of the periodic table, alkali metals and alkaline earth metals respectively, always form cations. Whether an atom forms a cation or an anion depends on its position on the periodic table. Predicting Cations and Anions based on the Periodic Table Ions like hydroxide, dichromate, sulfate, and ammonium that contain more than one type of element are called polyatomic ions and are discussed in more detail in another article. Because electrons are added to form an anion, the anion of an atom is bigger than the neutral atom.Įxamples of anions include the following: What is an anion? An anion is an ion that has gained one or more electrons, giving a net negative charge. Because one or more electrons are removed to form a cation, the cation of an atom is smaller than the neutral atom.Įxamples of cations include the following: What is a cation? A cation is an ion that has lost one or more electrons, giving a net positive charge. There are two types of ions: cations and anions.Ī cation has a net positive electrical charge, which means it has more protons than electrons.Īn anion has a net negative electrical charge, which means it has more electrons than protons. Ions are identified by a superscript that shows the sign and size of the electric charge – for example Ca +2. Ions form when atoms move into a more stable electron configuration. They contain different numbers of protons and electrons. The definition of an ion is a particle, atom, or molecule with an imbalance of electrical charge. Introduction to Ions, Cations and Anions What is an Ion? What are ions? In this tutorial, you will learn about the properties, differences, and examples of ions, cations and anions, as well as how to predict them based on their positions on the periodic table.
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