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