Periodic Trends

Chem 10 H

Chemical Reactions

Processes involving electron removal, electron addition, or electron sharing.

Valence Electrons

Electrons in the highest occupied principal energy level of an atom, directly involved in reactivity and compound formation.

Inner-shell (kernel) electrons

Electrons not directly involved in reactivity or compound formation.

Electron Dot Diagrams

Diagrams showing valence electrons as dots around an element symbol, used to track electrons during chemical bonding.

Octet Rule

Atoms tend to form compounds in ways that give them eight valence electrons, similar to noble gases.

Metals

Good conductors of heat and electricity, malleable, ductile, shiny, solid at room temperature (excluding Hg).

Nonmetals

Elements without metal properties, generally poor conductors, exist in all three states of matter.

Metalloids

Elements with properties intermediate between metals and nonmetals.

Periods and Blocks

Horizontal rows in the periodic table, length determined by the number of electrons occupying sublevels.

Atomic Radius

Size of an atom, generally decreases from left to right across a period and increases from top to bottom within a group.

Ionic Radius

Effective distance from the nucleus of an ion to its outer level of electrons, cations are smaller and anions are larger than their respective atoms.

Ionization Energy

Energy required to remove the most loosely held electron from an atom's valence level to form a positive ion.

Electron Shielding

Outer electrons are partially shielded from the attractive force of the nucleus by inner electrons.

Electronegativity

Measure of an element's electron attracting ability, increases across a period and decreases down a group.

Complete Exchange

When the difference in electronegativity between two elements is greater than ~1.7, a complete exchange of electrons occurs during compound formation.