bonding: any joining together of atoms or molecules
chemical bond or intramolecular bond: a strong bond between atoms or individual ions, resulting from the sharing or transfer of electrons
intermolecular bond: a weak bond between molecules or ions, which holds the molecules of a liquid or solid together. (We will study these in more detail later in the course.)
ion: an atom or group of atoms that has a charge, because it has either gained or lost electrons.
polyatomic ion: a group of atoms that are bonded to each other that behave chemically like a single ion. A polyatomic ion always has a specific formula and a specific charge.
For example: the sulfate ion has the chemical formula SO42−. It is made of one sulfur atom and 4 oxygen atoms. Chemically, it behaves like a single atom with a −2 charge.
ionic bond: when a positive ion and a negative ion are held together by the electrical attraction of their charges.
· ionic bonds occur between a metal and a non-metal.
· the positive ion (cation) is always either the ion of a metal or a positive polyatomic ion.
· the negative ion (anion) is always either the ion of a nonmetal or a negative polyatomic ion.
· the difference between the electronegativity of the nonmetal and the electronegativity of the metal (Δχ) is usually ≥ 1.7
covalent bond: when two atoms form a bond by sharing (“co-“) their valence (“-valent”) electrons.
· covalent bonds occur only between non-metals
· the electronegativity difference (Δχ) between the two nonmetals is usually < 1.7
metallic bond: when atoms in a metal form a network of positive ions and loosely held electrons.
· metallic bonds, as the name suggests, occur only between metals
· metallic bonds are often described as a “sea of electrons” because the valence electrons are free to move from one atom to another. This is how metals conduct electricity.