Basic Atomic Structure

group

Vertical column of elements in the periodic table

nonmetals

elements that are poor conductors of heat and electric current

metalloids

elements with properties that fall between those of metals and nonmetals

periodic law

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

periodic table

A chart of the elements showing the repeating pattern of their properties

orbital

A region in an atom where there is a high probability of finding electrons. An orbital can hold 2 electrons.

electron

A subatomic particle that has a negative charge and is found in the electron cloud outside an atom's nucleus. An electron has a mass of 1/1832 amu (very small mass!).

proton

A subatomic particle that has a positive charge and that is found in the nucleus of an atom. A proton has a mass of 1 amu.

neutron

A subatomic particle that has no charge and that is found in the nucleus of an atom. A neutron has a mass of 1 amu.

atomic number

Number of protons in an atom of an element. This number determines an element's identity.

mass number

Number of protons plus neutrons of an element.

subatomic particle

a particle smaller than an atom, such as a proton, neutron, or electron

ground state

a state in which all the electrons in an atom have the lowest possible energies

atomic mass unit

a unit of mass that describes the mass of a subatomic particle, an atom or a molecule

valence electron

an electron in the highest occupied energy level of an atom

electron cloud

area around the nucleus of an atom where the atom's electrons are most likely to be found

Ion

atom that has a positive or negative charge

metals

elements that are good conductors of electric current and heat

period

horizontal row of elements in the periodic table

electron configuration

the arrangement of electrons in the orbitals of an atom

energy levels

the possible energies that electrons in an atom can have

atom

the smallest particle of an element

isotopes

Atoms of the same element that have different numbers of neutrons. Isotopes have the same atomic number but different mass numbers.