Atomic number
Number of protons in an atom's nucleus.
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Periodic Table Essentials
Must-know chemistry table concepts.
school chemistry student
Flashcards
Mass number
Protons + neutrons in a nucleus.
Element
Substance of one type of atom.
Period
Horizontal row in the periodic table.
Group
Vertical column with similar properties.
Alkali metals
Group 1 metals (except hydrogen); highly reactive.
Halogens
Group 17; reactive nonmetals.
Noble gases
Group 18; mostly inert gases.
Valence electrons
Outer-shell electrons involved in bonding.
Ion
Atom or molecule with a net charge.
Isotope
Atoms of same element with different neutron counts.
Metal
Typically shiny, conductive, malleable element.
Nonmetal
Element that is usually a poor conductor.
Electronegativity
Tendency of an atom to attract electrons in a bond.