UNIT 3: Periodicity

Periodic Table

A list of all known elements arranged in order of increasing atomic number.

Period

A row of elements in the periodic table.

Group

Elements aligned vertically in columns in the periodic table.

Valence Electrons

Electrons in the outer shell of an atom.

s-block

Elements with only s electrons in the outer shell.

p-block

Elements with at least 1 p-electron in the outer shell.

d-block

Elements with at least 1 d-electron and at least 1 s-electron but no f or p electrons in the outer shell.

f-block

Elements with at least 1 f-electron and at least 1 s-electron but no d or p electrons in the outer shell.

Atomic Radius

The size of an atom, the distance between the nucleus and the outermost electron shell.

Ionic Radius

The size of an ion, the distance between the nucleus and the outermost electron shell of an ion.

Ionization Energy

The amount of energy required to remove 1 mole of electrons from 1 mole of atoms to form 1 mole of gaseous ions.

Electron Affinity

The amount of energy released when 1 mole of electrons is gained by 1 mole of atoms to form 1 mole of gaseous ions.

Electronegativity

The ability of an atom to attract an electron pair in a covalent bond.

Anions

Negative ions formed when atoms gain electrons.

Pauling Scale

A scale used to measure the value of electronegativity for each atom.

Oxide

A binary compound that contains oxygen and another element.

Amphoteric

Having the ability to react chemically as either an acid or a base.

Alkali Metals

Group 1 metals that form alkaline solutions with high pH when they react with water.

Halogens

Group 17 non-metals that are poisonous and form halide ions by gaining one more electron to complete the octet rule.

Density

The measure of how much mass is contained in a given volume of a substance.

Melting/Boiling Points

The temperature at which a substance changes from a solid to a liquid (melting point) or from a liquid to a gas (boiling point).

Reactivity

The tendency of a substance to undergo chemical reactions.

Electron Configuration

The arrangement of electrons in an atom or ion.

Valence Electrons

The electrons in the outermost energy level of an atom.

Electron Affinity

The energy change that occurs when an electron is added to a neutral atom to form a negative ion.

Atomic Radius

The distance from the center of an atom to the outermost electron shell.

Shielding

The effect of inner electrons blocking the attraction between the nucleus and outer electrons.

Electrostatic Forces

The forces of attraction or repulsion between charged particles.

Halogen Displacement

When a more reactive halogen displaces a less reactive halogen from a solution of its halide.

Displacement Reactions

Chemical reactions where one element replaces another element in a compound.

Potassium Bromide

A compound consisting of potassium and bromine ions.

Chlorine

A chemical element with the symbol Cl and atomic number 17.

Bromine

A chemical element with the symbol Br and atomic number 35.

Sodium Iodide

A compound consisting of sodium and iodine ions.

Iodine

A chemical element with the symbol I and atomic number 53.