Introduction to Atoms

period

a horizontal row of elements in the periodic table

chemical symbol

a one- or two-letter representation of an element

energy level

a region of an atom in which electrons of the same energy are likely to be found

neutron

a small particle in the nucleus of an atom, with no electrical charge

electron

a tiny, negatively charged particle that moves around the outside of the nucleus of an atom

periodic table

an arrangement of elements showing the repeating pattern of their properties

isotope

an atom with the same number of protons but a different number of neutrons from other atoms of the same element

proton

small, positively charged particles that are found in the nucleus of an atom

atomic mass

the average mass of all the isotopes of an element

atom

the basic particle from which all elements are made

nucleus

the central core of an atom which contains protons and neutrons

atomic number

the number of protons in the nucleus of an atom

mass number

the sum of protons and neutrons in the nucleus of an atom

group

elements in the same vertical column of the periodic table; also called family