World Book Trivia Quiz For Kids-5/22-chemical Elements

Elements can join with one another to form a compound. The compound may be very different from the elements that make it up.

A symbol is like an abbreviation. The symbol for oxygen is O and the symbol for hydrogen is H. Au, the symbol for gold, comes from aurum, the Latin word for gold.

Elements have symbols and numbers as well as names. A symbol is like an abbreviation. The symbol for oxygen is O and the symbol for hydrogen is H. Fe, the symbol for iron, comes from ferrum, the Latin word for iron.

Many chemicals contain two or more elements joined together. These chemicals are called compounds >. Water is a compound of hydrogen and oxygen. Salt is a compound of sodium and chlorine.

Pb is the symbol for lead.

Empedocles said that a force called love causes the elements to come together as compounds. He claimed that a force called strife (conflict) causes the compounds to break up.

An element's number, called its atomic number, tells something about its atom. Hydrogen's number is 1, because a hydrogen atom contains 1 proton. A proton is a piece of matter found within every atom. Oxygen's atom has 8 protons, so its number is 8.

Dmitri Ivanovich Mendeleev (1834-1907) was a Russian chemist who developed a form of the periodic law, a basic principle in chemistry. His law states that the properties of chemical elements recur in regular patterns when the elements are arranged according to their mass (amount of matter). Mendeleev's work, together with that of the German chemist Julius Lothar Meyer, led to the periodic table, a systematic arrangement of the elements.

There are 114 recognized elements, and each has its own kind of atom. Scientists believe there are still more to be discovered.

Barium nitrate makes signal flares and fireworks burn with a green flame.