vocabulary # 4

element : a basic building block of matter; a pure substance that  cannot be broken  down into any thing simplier.

compound : a chemical combination  of two or more elements into a single substance.

atom: the smallets unit of an element that still has the properties of the element.

proton : a particle with a positive  charge in the nucleus of an atom.

neutron: an uncharged particle in the nucleus of an atom.

electron : a particle with a negative charge moving around the nucleous of an atom.

nucleus :  the dense center part of an atom.

molecule: a group of more than one atom joined together that acts like a single particle.