atoms, elements, compounds, molecules and mixtures
an atom is the smallest invisible particle of matter
an element is a pure substance made up of only one type of atom
a compound is a pure substance made up of 2 or more elements. these elements are somehow chemically bonded together
a molecule is made up out of 2 or more atoms chemically bonded together
the 4 elements;
water
earth
air
fire
Atoms
An atom is the smallest indivisible particle of matter. All matter is made of atoms. All atoms are made of three subatomic particles: protons, neutrons and electrons. They are tiny! Trillions of them make up an eyelash.
Elements
An element is a pure substance that is made of only one type of atom. All of the atoms in an element are identical. A list of elements can be found on the periodic table.
More on Atoms!
An atom is the smallest 'bit' of an element. For example:
Gold is an element. Gold is made up of only gold atoms, bonded together.
This is a molecule of oxygen. It is two oxygen atoms bonded together. Oxygen gas has the chemical formula O2. Oxygen is also an element. It is made up of only oxygen atoms. This diagram shows two oxygen atoms bonded together. It is a diatomic element. (di=2). It is no longer an atom, but it is still an element.
A compound is a pure substance made up of two or more different elements. The elements in a compound are chemically together. For example:
Water is a compound. It consists of two hydrogen atoms bonded to one oxygen atom. This is a molecule of water. It is two hydrogen atoms bonded to one oxygen atom. Water has the chemical formula H2O.
Molecules
A molecule is made up of two or more atoms bonded together. These can be the same type of atom or different types of atoms. For example:
Both water and oxygen are molecules. Water consists of two different elements (hydrogen and oxygen) and oxygen only contains one element (oxygen).
Substances can be classified as either elements (one type of atom) or compounds (more than one type of atom) but not both.
However, a substance can be......
An element and a molecule
A compound and a molecule
An element and an atom
Chemical formulas
Chemical formulas show the type of atom (element) in a compound and the number of each type of atom. For example:
Compound
Formula
Type and number of atoms
Water
H2O
Hydrogen – 2 atoms, Oxygen – 1 atom
Carbon monoxide.
CO
Carbon – 1 atom, Oxygen – 1 atom
Methane
CH4
Carbon – 1 atom, Hydrogen – 4 atoms
Activity: Complete the Compounds worksheet on Canvas
Mixtures
A mixture is a combination of two or more pure substances. Mixtures are held together by physical forces, not chemical forces. No chemical change takes place. They can be separated.
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