Kimberly Miller, age 11, of Fairview, Oklahoma, for her question:

What causes rickets?

In most cases, this miserable disease is caused by poor diet and lack of sunshine. The wretched thing about rickets is that it strikes young children, usually those under 3. Medical researchers report that children who get plenty of calcium and vitamin D are less likely to get rickets. Some, however, may get the disease because their body chemistry is unable to make proper use of calcium and or vitamin D.

This miserable deficiency weakens bones and causes them to bend. Later, if the diet is improved, the bones will harden. But they do not become straight again and victims may spend the rest of their lives with bent bow legs or knobby knock knees. So let's drink .plenty of calcium¬ rich milk, eat plenty of vitamin D rich vegetables and get out in the sun. Vitamin D is also found in fish oil.

As in all atoms, the electrons are arranged in neat shells    and their number tells us something about the element's behavior. The inner electron shell, closest to the nucleus, is complete with two electrons. The second shell is complete with eight and the third with eighteen. The normal copper atom has three complete shells, plus one left over to start a fourth shell. This lone electron is prone to leave home.

Electricity is a current of moving electrons    and our electric wiring is made of copper. Voltage from a generator provides a jolt that frees zillions of lone electrons from the fourth shells of the copper atoms. They hop from atom to atom and their runaway energy is elect¬ricity.

Pure copper is made of nothing but copper atoms, which are all alike. As an element, it is classed with five others in the family of Third Transition Metals. The others are silver and gold, zinc and cadmium and mercury. Elements in this family have either three, four or five completed electron shells    plus either one or two electrons in an outside shell.