Elements and compounds
Select Lesson
Exam Board
Select an option
Chemistry practicals
Fuels and Earth science
Rates of reaction and energy changes
Groups in the periodic table
Extracting metals and equilibria
States of matter and mixtures
Key concepts
Chemical equations
Ionic equations and half equations - Higher
Hazards, risks and precautions
The history of the atom
The atom and isotopes
Calculating relative masses
Calculating relative atomic mass - Higher
The history of the periodic table
Electronic configuration
Ions and their formation
Ionic bonding: properties of compounds and naming
Covalent bonding
Giant covalent substances
Metallic bonding and alloys
Conservation of mass
Molecular and empirical formulae
Mole calculations and Avogadro's constant - Higher
Concentrations of solutions
Limiting reactants and masses - Higher
Practical skills
Explainer Video
Summary
Elements and compounds
In a nutshell
Elements are made up of the same type of atom. These elements are represented in the periodic table by one or two letters. A compound is formed when two different types of atoms are bonded together.
Elements
Definition
An element is made up of a single type of atom only. The type of atom is determined by the number of protons the atom contains in its nucleus. Atoms of the same element will have the same number of protons and therefore the same atomic number.
Example
A carbon atom contains six protons in its nucleus. Therefore, all of the atoms in the element carbon will contain six protons.
Elements in the periodic table
The periodic table is made up of elements. In total, the periodic table consists of different types of elements. Each element is represented in the periodic table by either one or two letters.
Examples
The element aluminium is represented in the periodic table by the symbol Al.
The element potassium is represented in the periodic table by the symbol K.
Compounds
Definition
A compound is formed when two or more different types of atoms join together and react to form a chemical bond. Compounds are formed from a reaction between two or more different elements.
Formulas to display compounds
To show compounds formulas are used. Formulas are made up from the symbols of each element (from the periodic table) that react together to form the compound. The formula of a compound will represent the proportion of each element that makes up the compound.
Example
The compound water is formed by reacting the elements hydrogen (symbol = ) and oxygen (symbol = ) together. A water molecule contains two hydrogen atoms and one oxygen atom, so the formula for water is .
Note: Brackets might be used along with little numbers outside of them to multiply several types of atoms held within the brackets.
Example
Brackets are used in magnesium nitrate, . Using the multiplication of the number of each type of nitrogen () and oxygen () atom inside the bracket by two, there is one magnesium atom, two nitrogen atoms and six oxygen atoms.
FAQs - Frequently Asked Questions
How are elements represented in the periodic table?
Each element is represented in the periodic table by either one or two letters.
What is a compound?
A compound is formed when two or more different types of atoms join together and react to form a chemical bond.
What is an element?
An element is made up of a single type of atom only.