Chapter 4

Atoms and the periodic table

Alkali Metal – One of the elements of group 1 (I) of the periodic table.

Alkaline Earth Metal – One of the elements of group 2 (II) of the periodic table.

Atomic Mass Unit (AMU) – A unit of mass that describes the mass of an atom or molecule; it is exactly one-twelfth of the mass of a carbon atom with a mass number of 12.

Atomic Number – the number of protons in the nucleus of an atom.

Average Atomic Mass – The weighted average of he masses of all naturally occurring isotopes of an element.

Avogadro’s constant – equals 6.022 x 10²³/mol ; the number of particle in a mol

Conversion Factor – a ratio that is derived from the equality of two different units and that canbe used to convert form one unit to another.

Electron- A subatomic particle that has a negative charge

Group or Family – A vertical column of elements in the periodic table.

Halogen – One of the elements of Group 17 (VII) of the periodic table.

Mass Number – The sum of the numbers of protons and neutrons in the nucleus of the atom.

Metal - An element that is shiny and conducts heat and electricity well.

Molar Mass - The mass in grams of 1 mol of a substance

Mole – The SI base unit used to measure the amount of a substance whose number of particles is the same as the number of atoms in 12 grams of carbon –12

Nucleus – An atom’s central region, which is made up of protons and neutrons

Neutron – A subatomic particle that has no charge and is found in the nucleus of the atom.

Noble Gas – An unreactive element of group 18 (VIII) of the periodic table

Nonmetal – An element that conducts heat and electricity poorly.

Period - A horizontal row of elements in the periodic table

Periodic Law – Law that states the repeating chemical and physical properties of an element change periodically with the atomic numbers of the element.

Protons – A subatomic particle that has a positive charge and is found in the nucleus of the atom.

Semiconductor – An element or compound that conducts electric current better than an insulator but not as well as a conductor.

Transition Metal – One of the metals of groups 3-12 of the periodic table.

Valence electron – an electron that is found in the outer shell of an atom and determines the atom’s chemical properties