Matching Pairs Atoms and APEMANOnline version Parts of the atom and APEMAN matching (8.5A) by James Dycus 1 M 2 3 4 E 5 A (M-A) 6 N 7 8 A 9 P 10 11 12 13 Electrons located in the outermost electron shell. This is the shell responsible for chemical reactivity. (Valence Electron) Number of Protons The dense and compact core of the atom that contains all of the protons and neutrons. (Nucleus) Number of Neutrons Subatomic particle with a neutral (0) charge and a mass of 1 atomic mass unit (1 amu) (Neutron) Circular areas that make up the electron cloud. These shells are the path that electrons take as they constantly move around the nucleus. (Energy Shells/Electron Shells) Subatomic particle that has a negative (-1) charge and has zero atomic mass units (0 amu) (Electron) Atomic Mass Area located outside of the dense compact core. This area is mostly empty space and is where all the electrons are located. (Electron Cloud) Atomic Number Number of Electrons Atomic Number (M-A) Subatomic particle with a positive (+1) charge and a mass of 1 atomic mass unit (1 amu) (Proton)