The 1)_________ is the smallest unit of matter that retains all the chemical properties of an element. It consist of three subatomic particles namely 2)______________, 3)_____________, and 4)_____________. The 5)___________ is located at the center of the atom that contains the protons and the neutrons. A proton is a 6)____________ particle that has a mass of 7)___________ discovered by 8)_______________ while a neutron has 9)___________ and
has a charge of 10)_____________ discovered by 11) ________________. A proton and a neutron are sometimes called 12)_______________.The outermost regions of the atom are by called 13)_______________ and contain the electrons. Electrons are 14)_____________ particles and have a mass of 15)_____________
