Atomic Structure

An atom, the smallest particle of an element that still retains the properties of that element, can be split up into smaller particles. Even long ago, they conceived that the atom could be divided into smaller parts. The problem was that they did not know exactly how they were split up. The ancient Greek philosopher, Democritus, thought that atoms were the smallest form of matter and were , therefore, indivisible. A man named John Dalton also believed atoms to be indivisible. Dalton also believed that atoms could not be created or destroyed.

As the question of how atoms are composed has ben risen many many times; so much that people have tried to explain how atoms look. A man named J.J. Thomson made a "plum pudding" model of what an atom looks like:

As you can see, the positive particles (protons) and the negative particles (electrons) are randomly spread out in the atomic space. Thomson was on the right track, but no cigar. A more accurate model was produced by a man named Ernest Rutherford:

Rutherford proposed that the negatively charged electrons orbited around a positively charged nucleus. While this is very very close, what's missing from this picture? Figure it out? That's right; there are not neutrons in the nucleus.

That's better. The orange, uncharged particles in the nucleus that are with the protons are the neutrons. They have no charge, but they add to the atomic mass of the atom. An atom of an element is characterized by its mass number and its atomic number. The mass number is the average mass of the most commonly found isotopes of an element found in nature. Isotopes are atoms of the same element with a different amount of neutrons. The atomic number is the number of the number of protons in the atom of that element. If two atoms have a different number of protons, they are atoms of different elements. If they have the same amount of protons, but different amount of neutrons, they're isotopes.