Atoms and Ions

Everything, non and living is made of small things named Atoms.

At the basic structure, an atom is a Nucleus surrounded by-elections which orbit around the Nucleus in rings called shells,
the nucleus of an atom is made out of two things Protons, and Neutrons, both having very similar weight, but electricians are nearly 2000 times lighter than protons or neutrons.

Protons have a +1 charge, while neutrons have no charge, so they are neutral, and electrons have a -1 charge.
The size of an atom depends on the type of element they are, but most are 0.1 nanometers in size, for example, the average size for a penny is 19.55mm, which is equal to 19,050,000 nanometers).
Most atoms are empty space because we measure the size of an atom starting from the nucleus to the outermost shell.

The nucleus is 10,000 times smaller than the size of the whole atom,
if an atom has the same number of Protons and Electrons, the atom thus, neutral.
But when an atom gains an election it is named a Negative Ion or Anion since there are more electrons than protons, this is called a -1 negative ion, and if you add another election it would be a -2 negative ion. 

Then if an atom has fewer electrons than protons (3 protons 2 electrons), it would be a +1 ion.
An atom on the periodic table is an Element, and each box on the periodic table has an element, each box is named a 'Nuclear symbol". 

Let's take two elements: Oxygen and Lithium, the Li and O on the box are the elemental symbols, then in the bottom left corner of the element is the Atomic number which tells us how many protons the atom has, so an Oxygen atom has 8 protons while a Lithium atom has 3.

The top number is the Mass number, which tells us the total amount of Protons and Neutrons the element has.
Now let's use a lithium atom for example, so a Li element or lithium will have a 7 as its mass number and a lithium atom has 3 protons, so if you do 7 - 3 protons, you get the number of neutrons a lithium atom has which is 5 neutrons. 

An oxygen atom has a mass number of 16, and its amount of protons is 8 so 16 - 8, is 8 so it has 8 neutrons. Or to get the amount of neutrons you do the mass number minus the atomic number.