Protons, Neutrons, and Electrons

Atomic number

The number of protons in the nucleus of an atom

Electron cloud

The region surrounding an atomic nucleus where electrons may be found

Atoms

The smallest unit of an element that has all chemical properties of that element

Nucleus

The core of an atom exists; contains protons and neutrons

Subatomic

Of or relating to something having dimensions smaller than that of an atom

Period

One of the horizontal rows in the periodic table

Periodicity

Reoccurring pattern of similar chemical and physical properties of elements which are close to each other in the periodic table

Atomic mass unit (amu)

A unit of mass that is equal to 1/12 the mass of a Carbon 12 atom

Mendeleev

A Russian scientist who organized and classified the elements based on similar physical and chemical properties; his work was the basis for the modern periodic table of the elements

Negative charge

A charge of the same sign as that of an electron, often because of a surplus of electrons

Positive charge

A charge of the same sign of a proton because of a deficit of electrons

Electron

A negatively charged subatomic particle that exists in various energy levels outside the nucleus of an atom

Element

A pure substance that cannot be broken down into simpler substances by chemical reactions

Proton

A subatomic particle with a positive charge that is located in the nucleus of an atom and has a mass of about one amu

Neutron

A subatomic particle with no electric charge that is located within the nucleus of the atom and has a mass of about one amu

Isotope

An atom of the same element with the same number protons but different number of neutrons; has the same atomic number but different atomic mass number

Anion

An atom that has gained electrons so has a negative charge

Cation

An atom that has lost electrons so has a positive charge

Ion

An atom that has lost or gained electron(s)

Average atomic mass

The weighted average of the atomic mass of each isotope of the element, in proportion to the percentage of each isotope of the element occurring in nature

Mass number

Total number of neutrons and protons in an atom; aka nucleon number

Family/group

Vertical columns of elements on the periodic table with similar valence electron configurations and similar properties