Select an element to design. Remember that each element's atomic number dictates the number of protons, electrons and neutrons present in one of its atoms.
Use a 2-inch foam ball for each proton, a 1.5-inch foam ball for each neutron and a 1-inch foam ball for each electron. If assembling a model of a carbon atom -- atomic number of 6 -- you will need six of each sized foam ball.
Paint each ball according to the particle it represents. Protons could be painted red while neutrons are painted blue and the electrons yellow. Use your imagination when selecting colors, as they can be painted any color you like. Set them aside and let them dry before assembly.
Assemble your nucleus first. Glue the protons and neutrons together in an alternating fashion -- because they are of different charges, protons and neutrons alternate in position when stacked close together, first in a triangular shape and then forming a more spherical shape as the atomic number rises.
Straighten a wire hanger and cut two 4-inch lengths out of it. These will suspend your first two electrons from the nucleus, as the first electron energy level in the electron cloud surrounding the nucleus holds only two electrons. For each subsequent energy level, extend the length of wire by 1 inch -- the second level measures 5 inches and the third 6 inches -- level 6 should measure 9 inches. Use more than one wire hanger if necessary.
Insert each length of wire 1/2 inch into each electron and 1/2 inch into a proton or neutron in the nucleus. For elements with atomic numbers greater than 2, the second electron energy level holds eight electrons, the third holds 18, the fourth holds 32, the fifth holds 50 and the sixth holds 72.
Label one of each subatomic particle by writing its name -- proton, neutron, or electron -- on one of your 1-by-3 paper rectangles. Tape or glue each of your labels onto a toothpick and then stick the other end of the toothpick into the corresponding subatomic particle. To label the atom itself, created a banner of sorts by writing the element's name on one of your labels and attaching it between two toothpicks, then stick the name banner into the nucleus.