Rocks and building (including quite a bit on atomic structure)
All substances are made of atoms.
The atoms themselves contain a nucleus (containing protons and neutrons) surrounded by electrons.
An atom is the smallest particle that can be recognised as being an element.
The periodic table shows a list of elements.
The elements are substances that only contain one kind of atom.
Atoms of elements have a chemical symbol. The first letter is always a capital letter. The second letter (if it has one) is always a lower case. Be careful that your handwritten lower case “l” does not look like a capital “L”.
The periodic table collects elements with similar properties in vertical columns called groups.
Atoms join together (bond) by gaining, losing or sharing electrons to form compounds.
The chemical formula of a substance shows the number of each kind of atom that are joined together. For an ionic compound, the formula shows the ratio of each kind of atom.
In any chemical reaction, the total mass of the starting materials (reactants or reagents) is always the same as the total mass of the materials at the end (products). Sometimes you might be confused in this because some substance may be added or taken away that are not included in your weighings.
Chemical equations (symbol ones) must always be balanced. That is they must have the same number of each kind of atom on both sides.
Limestone is a building material. It has the chemical name calcium carbonate.