Venus Buckwalter, age 12, of Merrillville, Indiana, for her question:

Why is copper such a good conductor?

Electricity is the energy of runaway electrons that normally orbit the nucleus of the atom. The atoms of each element have a fixed number of positive protons in the nucleus and an equal quota of negative electrons. However, certain electrons may be loosely attached and likely to leave home. These energetic runaways create the current in our copper electrical wire. Other metals also can conduct current, but copper has proved most suitable.

Its useful quality depends on numbers and organization. The copper atom, with 29 protons has a quota of 29 electrons. As in all atoms, they are arranged in shells around the nucleus. The number allowed in each shell is precise. In copper, the inner shell has two and the second has eight. The third shell is completed with eighteen. This happens to leave one electron loosley attached in an outer shell. Voltage from a generator jolts zillions of these lone rangers from their copper atoms. They create and conduct current through the wires.