Students are usually fairly comfortable with the idea that the number of electrons and protons in a standard atom is equal. They are also usually able to memorize quite quickly that the electrons are arranged in concentric orbits that fill up from inside to out, with two electrons in the first ring and eight in each subsequent ring. However, practice is sometimes need to set this idea firmly in their minds. Print out a set of sheets with the nuclei of different elements in the center using circles of one color for the neutrons and one for the protons. Little plus signs on the protons can help. Add sets of empty rings around each nucleus. Hand the cards out, one to each student, along with a pot of beads. Give them 20 seconds to arrange the beads on the orbits to balance with the number of protons in the nucleus. Get each student to check their neighbor's then pass the cards around and have them do it again. This activity is good for about 10 to 15 minutes.
The next step in understanding electron configuration comes from understanding that atoms "want" complete outer shells of electrons; that is they want their outer orbit to contain eight electrons, or two in the case of the innermost ring. They can achieve this by giving away all the electrons on the outer shell to other atoms or taking electrons from another atom to complete their outer shell and form ionic bonds. This means that certain atoms naturally pair up with others. Provide some cards with the atoms that make up simple, familiar compounds such as sodium chloride. Draw the atoms in the same way as the atoms in the previous step, but this time include the electrons. Put all the cards out and have the students race to see if they can find elements that would naturally pair because one wants to gain the same number the other loses.
It's a useful, general rule in chemistry that atoms are lazy and those that need to do the least work -- i.e. gain or or lose the fewest number of electrons -- to get their full outer shell are more likely to react than those that need to do more work. Knowing this the students should be able to sort the cards into the most reactive at the top and the least at bottom. Give each student a stack of randomly chosen cards and have them sort them by reactivity. Explain also that losing electrons gets harder the closer the outer shell is to the nucleus, while gaining them gets easier. Have them sort the atoms by reactivity using this rule as well. Once they are quick enough, run a championship to see which student can sort a stack of 20 atom cards the fastest.
Make some cardboard rings that can be worn on the head and some stickers with electron or proton written in them. Make sure you have an equal number of each. Go out into the school yard and draw some rings on the ground with different elements written in each. Give each student a ring and a sticker. Have them try and sort themselves into atoms as fast as possible. They need to get the right number of protons in the ring with the right number of electrons around them organized into the correct configurations.