Objective 6: Students will be able to list the properties of the three major subatomic particles.
The atom is composed of two regions. At the core is a nucleus that takes up very little room but counts for most of the solid mass of the atom. Surrounding it is the electron cloud, a much larger space in which the almost-weightless electrons move swiftly and randomly.
The nucleus is composed of two kinds of particles-- positively charged protons and neutrally charged neutrons. Both contribute to the mass of the atom, but only the protons help to identify the atom. The protons repel each other violently, but a powerful nuclear force helps to keep the nucleus together.
In the electron cloud the electrons occupy specific regions defined by how much energy they possess, but inside those regions they move so fast that they appear to be everywhere at once. Electrons determine the chemical properties of a substance.
Much of the information every serious chemistry student needs to know about the subatomic particles is summarized below.
Location Mass Symbols Relative
Charge
Mass Number Major
Contributions
Proton nucleus 1.65 x10 -24 g p + ' +1 1 AMU Mass, identity
Neutron nucleus 1.67 x10 -24 g n 0 0 1 AMU mass
Electron electron cloud 9.11 x10 -29 g e - -1 0 AMU Volume, chemical properties
Practice: Answer each of the following questions. Rehearse them until you can answer them without looking at the chart.
Which sub-atomic particle(s) account for the mass of the atom?
Which subatomic particle(s) give the atom negative charge?
Which subatomic particle(s) reside outside the nucleus?
Which subatomic particle(s) give the atom its volume?
Which pair of subatomic particles weigh approximately the same?
Which pair of subatomic particles have an electric charge?
Which subatomic particle(s) account for an atom's chemical properties?
Which subatomic particle(s) give an atom its identity?

More Practice: p. 74 #1, 3. p. 87 #3.