A substance that cannot be broken down into simpler substances by chemical means.

The smallest unit of an element that keeps the element’s chemical properties.

The dense center of an atom containing protons and neutrons.

Positively charged particles found in the nucleus of an atom.

Particles with a neutral charge found in the nucleus of an atom.

All known elements arranged in order by atomic number.

Vertical columns of elements that have the same amount of valence electrons.

Horizontal rows of elements that have the same number of electron shells. 

The average number of protons and neutrons in one atom of an element.

Elements that are malleable, ductile, and good conductors; typically shiny.

A substance that cannot be broken down into simpler substances by chemical means.

The smallest unit of an element that keeps the element’s chemical properties.

The dense center of an atom containing protons and neutrons.

Positively charged particles found in the nucleus of an atom.

Particles with a neutral charge found in the nucleus of an atom.

A negatively charged subatomic particle located around the nucleus of an atom.

Areas around the nucleus filled with electrons. 

The electrons filling the outermost shell; react with other atoms.

A substance formed from two or more atoms chemically united in fixed proportions.

A group of atoms held together by chemical forces.