Atoms and molecules

Atoms and molecules
The tiny particles that make up elements are called atoms. An atom is the smallest unit of an element that retains or keeps the properties of that element. For example, the atoms that make up oxygen can never be changed.
The inside of an atom contains three different kinds of particles as well. They are called protons, neutrons, and electrons. Surprisingly, atoms are not solid, they are mostly empty space. There is a tiny, very dense body in the center of an atom called the nucleus. Inside the nucleus are the protons and neutrons. The electrons are in the space outside the nucleus.
A proton carries one unit of positive electric charge. An electron carries one unit of a negative electric charge. Neutrons have no electric charges. The number of protons in an atom determines what the element is. An oxygen atom, for example, has eight protons.
The Periodic Table of Elements shows the number of protons for each element. The element or substance called sodium has eleven protons. Sodium is a substance when combined with another substance makes salt. As in all kinds of matter, the different elements can be a solid, liquid, or gas.
The different kinds of atoms are then joined together to make a molecule. A molecule is a particle that contains more than one atom joined together. Basically, atoms come together in different ways to make molecules, and molecules come together in different ways to make different kinds of matter.