Valence Electrons and Ionic Compounds

Valence Electrons and Ionic Compounds

Valence Electrons

  • Valence electrons are the electrons in the outermost energy level of an atom that participate in chemical bonding.
  • Atoms with the same number of valence electrons have similar properties and belong to the same group (or column) in the Periodic Table.
  • They are important because they are the electrons involved in forming chemical bonds with other atoms.
  • Valence electrons can be determined by the group number of the atom in the periodic table. For instance, all alkali metals (Group 1) have one valence electron, while all noble gases (Group 18) have eight (helium has two).
  • The number of valence electrons affects the reactivity of an atom. Atoms with few valence electrons tend to lose them and become positive ions (cations), while atoms with nearly full outer energy levels tend to gain electrons and become negative ions (anions).

Ionic Compounds

  • Ionic compounds are formed when a metal transfers one or more electrons to a nonmetal in an effort to fill their valence shells. This results in ions with opposite charges that attract and form a crystal lattice structure.
  • When an atom loses or gains electrons, it becomes an ion. If it loses electrons, it has more protons than electrons, so it has a positive charge and is called a cation. If it gains electrons, it has more electrons than protons, so it has a negative charge and is called an anion.
  • The formula for an ionic compound is the simplest ratio of the compound’s positive ions (cations) and negative ions (anions). This known as the empirical formula.
  • Ionic compounds have high melting and boiling points due to the strong attraction between the ions. They are typically solid at room temperature and can conduct electricity when dissolved in water or molten.
  • Common examples of ionic compounds include sodium chloride (NaCl), potassium iodide (KI), and calcium carbonate (CaCO₃).
  • In naming ionic compounds, the metal ion’s name stays the same while the nonmetal ion’s name ends in ‘-ide.’ For example, the ionic compound of Na⁺ and Cl⁻ ions is named sodium chloride.