Hi there Laura. That's great that you're introducing your daughter to the field of chemistry. There are so many neat things about the elements that I'm sure she'll really like. If you click on the Periodic Table link over on the left, you'll be able to see a picture of all the elements on the periodic table. If you are looking for a specific type of photograph, just let me know and I can take some more photographs of my elements and send them along to you.
Anyway, lithium metal is an alkali metal in group 1A of the periodic table. All of the metals in this group are VERY reactive metals for numerous reasons. Each of the metals will react with oxygen to form the metal oxides, and they react with water to form metal hydroxides and hydrogen gas. The further down the column you go, the more violent the reaction is. In water, lithium slowly fizzes and dissolves forming a solution of lithium hydroxide. Sodium metal reacts more vigorously and tends to catch fire and some times explode. Potassium will always catch fire and usually explodes. Rubidium will catch fire upon exposure to the atmosphere and explodes violently in water. Cesium will also catch fire if exposed to a normal atmosphere and reacts incredibly quickly with water.
In addition to reacting with oxygen/water, lithium will also react with nitrogen in the air forming Lithium nitride. The oxidation caused by reactions with atmospheric moisture and oxygen, in addition to nitrogen, turns lithium into a dull and dark gray color. The lithium picture I have on the periodic table here has a slight bit of the dark oxidation which can be seen if you look closely.