They are the furthest electrons from the nucleus.Ī prime example of a covalent bond is the hydrogen molecule, which forms from two hydrogen atoms, each with one electron in their outer shell. Bond formation releases heat therefore, it is exothermic. This property represents the electrons of an atom that can participate in the formation of chemical bonds with other atoms. The number of covalent bonds an atom can form is called the valence of the atom. Electronegativity, denoted by the symbol χ, is a chemical property that describes the tendency of an atom to attract a shared pair of electrons (or electron density) towards itself. Covalent bonds, also called molecular bonds, only form between nonmetal atoms with identical or relatively close electronegativity value. What’s more, each ion has a complete electron shell that corresponds to the nearest inert gas neon for a sodium ion, argon for a chloride ionĬovalent bonds form when atoms or ions share electrons such that their outer shells become occupied. Now, in the resulting crystal structure, each sodium ion is surrounded by six chloride ions and each chloride ion is surrounded by six sodium ions. When the two atoms react, sodium (electropositive) loses its valence electron to chlorine (electronegative). Chlorine is made up of 17 protons and 17 electrons, and has 7 electrons in its outer shell. A single sodium atom has 11 protons and 11 electrons, but only a single electron in its outer shell (or valence shell). Therefore, ions combine in ways that neutralize their charges.Ī textbook example of an ionic compound is sodium chloride, also known as table salt. Chemists refer to such ions as anions (non-metals). On the other hand, gaining electrons grants the ion a negative charge. Ions that loss one or more electrons have more protons than electrons, which means they have a positive charge.
An ionic bond forms when two ions of opposite charges exchange electrons between them, where an ion is an atom that has either lost or gained an electron.
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