Mendeleev

Moseley

Periodic Law

when the elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties

Period

a horizontal row of elements in the periodic table

Group / Family

a vertical column of elements in the periodic table; the constituent elements of a group have similar chemical and physical properties

Alkali Metals

any metal in Group 1A of the periodic table

Alkaline Earth Metals

any metal in Group 2A of the periodic table

Halogen

a nonmetal in Group 7A of the periodic table

Nobel Gases

an element in Group 8A of the periodic table; the s and p sublevels of the highest occupied energy level are filled

Metals

one of a class of elements that are good conductors of heat and electric current; metals tend to be ductile, malleable, and shiny

Non-metals

an element that tends to be a poor conductor of heat and electric current; nonmetals generally have properties opposite to those of metals

Semimetals / Metalloid

an element that tends to have properties that are similar to those of metals and nonmetals

Valence Electrons

an electron in the highest occupied energy level of an atom

s, p, d, f blocks

atomic radius

one-half the distance between the nuclei of two atoms of the same element when the atoms are joined

ionic radius

ionization energy

the energy required to remove an electron from an atom in its gaseous state

Electronegativity

the ability of an atom to attract electrons when the atom is in a compound

Transition Metals

one of the Group B elements in which the highest occupied s sublevel and a nearby d sublevel generally contain electrons

Lanthanide Series

Actinide Series

Diatomic Elements

(Molecule)

a molecule consisting of two atoms