Subatomic Particles The atom is composed of three main subatomic particles: _____________, _______________, and, _________________________ Table 1. Mass, charge, and location of the three subatomic particles. Particle Label the atom Charge Mass (atomic mass units or amu) Electron Proton Location Neutron Nucleus Each element is defined by it's number of protons. This can be seen in the atomic number. Atomic Number: ­ Elements are organized in the periodic table according to their atomic number ­ the atomic number of an element ________ it's number of protons. How many protons do the following elements have in their atoms? Mg: ________ silicon: ___________ Fe: ___________ 1 Atomic Mass: ­ This is the average _______ of the atom Which two subatomic particles have the most mass? Atomic mass = # of _____________ + # of ___________ Also to find the number of neutrons, rearrange to get # of neutrons = ___________________ ­ ________________ ­ The atomic mass is not always a whole number, as it is an average of all of the atom's naturally occurring isotopes. ­ The term isotope refers to different forms of an element that have the same number of protons but different number of neutrons. Ex: 13 C or carbon­13 To find number of electrons We will be dealing with atoms that are neutral. Therefore there must be the ____________ number of protons as electrons. number of electrons = number of protons = atomic number For each of the following, find the number of protons (p), electrons (e), and neutrons (n). Na: p = e= n= copper: p = e= n= S :p= e= n= aluminum: p = e= n= 2