CIR Room 9: IONIC SIZE AND ELECTRONEGATIVITY

Electronegativity

- chemical property that describes the ability of an atom (or, more rarely, a functional group) to attract electrons (or electron density) towards itself

- a measure of the tendency of an atom to attract a bonding pair of electrons.

- affected by both its atomic number and the distance that its valence electrons reside from the charged nucleus. The higher the associated electronegativity number, the more an element or compound attracts electrons towards it

- increases on passing from left to right along a period, and decreases on descending a group.

Ionic Size

- Ionic size is the size of the atom after it loses its outermost electron (after the first Ionization Energy).

- When atoms gain or lose electrons, the atom becomes an ion. When an atom gains an electron, it becomes a negatively charged ion that we call an anion. Anions are larger in size than their parent atoms because they have one or more additional electrons, but without an additional proton in the nucleus to help moderate the size

- When an atom loses an electron, it becomes a positively charged ion called a cation. Cations are smaller than their parent atoms because they have lost electrons (sometimes the entire outermost energy level) and the electrons that remain behind simply don't take up as much room.

- Also note that when comparing cations and anions, the anions are larger.