2.3 Elements can combine form compounds

a substance consisting of two or more different elements combined in a fixed ratio

carbon, hydrogen, oxygen, nitrogen

The smallest unit of matter that still retains properties of an element

a particle with one positive electrical charge

a subatomic particle with a single negative electrical charge

an electrically neautral atom

an atom's central core

the attraction between between the - charged electrons and the + charged protons

atoms of a particular element have the same unique number of protons

the sum of the protons and neutrons in the nucleas

equal to it's mass number, the sum of protons and neautrons

have the same numbers of protons and electrons and behave identically, but they have different numbers of neautrons

When the nucleus decays spontaneously giving off particles and energy.