An expository essay.

All matter consists of molecules, which consist of atoms, which consist of protons, neutrons, and electrons. All electromagnetic waves consist of photons.

Although the molecule is the biggest particle I am mentioning in this essay, it is still very tiny. Molecules are made up of two or more atoms. According to the kinetic-molecular theory, molecules are in constant motion. The state in which matter appears (solid, liquid, or gas) depends on the speed and separation of the molecules of this matter. Substances differ according to the structure and composition of their molecules.

A molecular compound is represented by its molecular formula; for example, water is represented by the formula H₂O. Molecules differ in size and molecular weight as well as in structure. In a chemical reaction, the molecules are often broken apart into atoms or radicals that recombine to form other molecules of other substances. In other cases two or more molecules will combine to form a single larger molecule, or a large molecule will be broken up into several smaller molecules.

The next smallest particle is the atom. The atom consists of a nucleus, and it’s orbiting electrons. All atoms are about the same size, weather they have 3 electrons or 90 electrons. The radius of an atom measures about 10 ^-10 meter, which means that about 50,000,000 atoms lined up in a row would measure one centimeter. The atom is mostly empty. If the nucleus were the size of a marble, the whole atom would be 300 feet across. The diameter of a nucleus is different for different atoms, the smallest is about 10 ^-10 meter.

The electron is a very light particle. It’s mass is 9.11*10 ^-31 kg. The electron is a very interesting thing. It sometimes acts as a particle, and sometimes as an electro magnetic wave. When a photon hits the outer electron, the electron jumps from it’s orbit onto another and releases photons of certain frequency. That is how we see objects in different color. The electron has a negative electric charge.

The nucleus consists of neutrons and protons. Both are heavy particles compared with an electron and are about 1,836 times more massive than an electron, but proton has a positive electric charge, while neutron does not. The electron is attracted to the nucleus because it has a different charge then proton, but why it does not fall on it, this I do not understand.

The protons and neutrons are made up of quarks, which I do not know much about.