Biology, Answering the Big Questions of Life/Atoms and Molecules
What is the world made of?[edit | edit source]
The ancient Greek philosophers studied the nature of all things.
They wanted to know what things were made of. They knew that the things in the world had substance. They take up space. You can touch them and push against them. They called this substance that all things are made of matter.
Matter is defined as any substance in the universe that has mass and occupies space.
Mass is a measure of how much matter there is in an object. On earth we measure mass by weighing an object. Weight, however can change. A person who weighs 180 pounds on the Earth would only weigh about 30 pounds on the moon even though their mass would stay the same.
But these philosophers wanted to know what the fundamental things were that the universe was built of. If you take an object and cut it in half, and then cut that object in half, eventually you should get to some thing that you can't cut. Something that is the building block that all things are made of. They called this the 'atom', which comes from the Greek prefix a which means not and the root tom which means to cut.
In the fifth century B.C. two philosophers, Democritus and Leucippus presented the first theory of atoms, however it took humans almost two an a half millennia to find out the structure of the atom.
What is an Atom?[edit | edit source]
An atom is the smallest component of an element that still has the properties of that element.
Atoms are made of three particles. protons, neutrons, and electrons. The protons and neutrons reside in the center of the atom, called the nucleus, while the electrons circle around them.
The protons have a positive charge and the neutrons have no charge. They make up the bulk of the weight of the atom. Around the nucleus, small charged particles called electrons move in complicated patterns called orbitals.
The discovery of the structure of the atom changed how we looked at the world. For one, it explained chemistry. Chemical reactions are interactions between the electrons on the surface of atoms. The properties of atoms are directly related to the number of protons found in their nucleus, which determines the number of electrons.(In normal matter you have one electron for every proton). The variation between different types of atoms such as hydrogen, which is very reactive, and helium, which is not, is directly related to the fact that hydrogen has one proton in its nucleus and helium has two.