The negative ion that results when an atom gains one or more electrons. An anion (pronounced "AN-ie-un") of an element is never called, for instance, the chlorine anion. Rather, for an anion involving a single element, it is named by adding the suffix -ide to the name of the original element—hence, "chloride." Other rules apply for more complex anions.
The smallest particle of an element. An atom can exist either alone or in combination with other atoms in a molecule.
The number of protons in the nucleus of an atom. Since this number is different for each element, elements are listed on the periodic table of elements in order of atomic number.
The energy required to pull apart the atoms in a chemical bond.
The positive ion that results when an atom loses one or more electrons. A cation (pronounced "KAT-ie-un") is named after the element of which it is anion and thus is called, for instance, the aluminum ion or the aluminum cation.
The joining, through electromagnetic force, of atoms representing different elements. The principal types of bonds are covalent bonding and ionic bonding, though few bonds are purely one or the other. Rather, there is a wide range of "hybrid" bonds, in accordance with the electronegativity values of the elements involved.
A one-or two-letter abbreviation for the name of an element.
A substance made up of atoms of more than one element. These atoms are usually joined in molecules.
A type of chemical bonding in which two atoms share valence electrons. Atoms may bond by single, double, or triple covalent bonds, which, in representations of Lewis structures, are shown by single, double, or tripledashed lines. (The double dashed linelooks like an equals sign.) When atoms have differing values of electronegativity, they form polar covalent bonds.
A term describing the distribution of valence electrons when hydrogen atoms—which end up with only two valence electrons—experience chemical bonding with other atoms. Most other elements follow the octet rule.
Negatively charged particles in an atom. Electrons, which spin around the protons and neutrons that make up the atom's nucleus, are essential to chemical bonding.
The relative ability of an atom to attract valence electrons.
A substance made up of only one kind of atom. Unlike compounds, elements cannot be broken down chemically into other substances.
An atom that has lost or gained one or more electrons, and thus has a net electrical charge. Ions may either be anions or cations.
A form of chemical bonding that results from attractions between ions with opposite electricalcharges.
A means of showing schematically how valence electrons are distributed among the atoms in a molecule. Also known as the electron-dotsystem, Lewis structure represents pairs of electrons with a symbol rather like a colon, which—depending on the situation—can be placed above, below, or on either side of the chemical symbol. In the Lewis structure, the pairs of electrons involved in chemical bonds are usually represented by a dashed line.
A group of atoms, usually, but not always, representing more than one element, joined in a structure. Compounds are typically made of up molecules.
A subatomic particle that has no electrical charge. Neutrons are found at the nucleus of an atom, alongside protons.
The center of an atom, a region where protons and neutrons are located, and around which electrons spin.
A term describing the distribution of valence electrons that takes place in chemical bonding for most elements, which end up with eight valence electrons. Hydrogen is an exception, and follows the duet rule. A few elements follow other rules, and some (most notably the noble gases) do not typically bond with other elements.
A chart showing the elements arranged in order of atomic number. Vertical columns within the periodic table indicate groups or "families" of elements with similar chemical characteristics.
The type of chemical bonding between atoms that have differing values of electronegativity. If the difference is extreme, of course, the bond is not a covalent bond at all, but an ionic bond. Thus, although these are sometimes called polar bonds, they are more properly identified as polar covalentbonds.
A positively charged particle in an atom.
Electrons that occupy the highest energy levels in anatom. These are the only electrons involved in chemical bonding. By contrast, the coreelectrons, or the ones at lower energy levels, play no role in the bonding of atoms.
The property of the atom of one element that determines its ability to bond with atoms of other elements.