Inside Atoms
What are atoms?
Atoms are the building blocks that everything is made out of.
An element like a gold bar will be made out of gold atoms. They would be the same throughout the block.
Atoms are made up of little particles called protons, neutrons and electrons.
Protons and neutrons are found in the nucleus while electrons are found in shells around the nucleus.
Protons
Protons are positive particles. They have a charge of +1.
They are found in the nucleus of an atom.
They have a mass of 1
Neutrons
Neutrons are also found in the nucleus. They have no charge so we call them neutral, it is given the symbol of 0.
Neutrons also have a mass of 1 like protons.
Electron
Electrons are found in the shells around the nucleus.
They are a lot smaller than protons and neutrons.
They are negative and have a charge of -1
They have a mass of 0.0005
Every element in the periodic table has a card like the one on the left. It shows the elements symbol and two numbers. The symbol is either ONE capital letter or ONE capital and ONE lower case. It is never two capitals (that would be a compound) or two lowercase.
The mass number which is the bigger number is usually at the top. This is the number of protons AND neutrons together
The bottom number is called the atomic number or proton number. This is the smaller number and is usually at the bottom.
Because the number of positives and negatives is the same, it can also tell us how many electrons there are.
Working out the numbers
We know Helium is the element on the card.
The atomic number (bottom number) or proton number is 2. That means it has 2 protons.
Because protons and electrons are always the same it must have 2 electrons.
It has a mass number (top number) of 4. That means that it has a total of 4 protons and neutrons together. We know it has 2 protons.
4 – 2 = 2 so it must have 2 neutrons.
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