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A molecule consists of two or more atoms that bond by sharing their outer electrons. The molecules below are Lewis Structures.

Oxygen gas (O2) and water (H20) are examples of molecules.

Description: Oxygengas2 Description: Water Molecule


Some Common Molecules drawn as Lewis Structures:

Fluorine Gas F2

Oxygen Gas O2

Hydrogen Gas H2

Ammonia Gas NH3

Nitrogen Gas N2

Hydrochloric Acid - HCl

Water H2O

Hydrogen Peroxide H2O2

Silicon Dioxide SiO2

Methane Gas CH4

Acetylene Gas C2H2

Ethylene Gas C2H4


Atom = The smallest unit of matter; The basic unit of a chemical element. For example, Water (H2O) is made up of three atoms.


Compound = a chemical substance that is formed from two or more elements, that bond in a fixed ratio. For example, water (H2O) is a compound that is composed of two hydrogen atoms for every oxygen atom. NH3, HCl, H2O2, SiO2, CH4, C2H2, and C2H4, are compounds. In contrast, O2 is not a compound because it is only made of one element. A compound is a pure substance.

Covalent Bonding is where 2 or more atoms bond by sharing their outer electrons. Generally, covalent bonds are made between nonmetal atoms. The result of this bond is a molecule. Covalent means, "Sharing outer electrons". The nucleus of an atom is never changed or altered after bonding. Covalent bonding allows atoms to complete their outer shells.

Electrons are stable subatomic particles that have a negative charge. They can be found in the shells of atoms outside the nucleus. A pair of electrons form a covalent bond between atoms.

An element is composed of one kind of atom. An element is a pure substance. An element cannot be broken down by physical or chemical means. 90 elements occur naturally on Earth. The other 19 or so are made in the lab. This means that in the universe, there are only 90 different types of atoms that make everything. C, H, O, N and P are the primary elements that make up living organisms.

The octet rule states that after bonding...

1) 8 electrons surround all atoms in columns 4-7. (After bonding)

2) Hydrogen's outer ring is completed with 2 electrons. (After bonding)

3) All atoms have a complete outer ring. All electrons are paired up. (After bonding)

4) All atoms have a complete outer ring like noble gasses. (After bonding)

In summary: Atoms share or transfer their electrons with other atoms to complete their outer ring and be like the noble gasses.

Protons are stable subatomic particles that are found in the nucleus of all atoms. Protons have a positive charge and counteract the charge of electrons. The number of protons in the nucleus determines what the element is. For instance, atoms with one proton are the element hydrogen. Atoms with 8 protons are the element of Oxygen.

Neutrons are a subatomic particle of about the same mass as a proton but without an electric charge, present in all atomic nuclei except those of ordinary hydrogen.

Subatomic Particles = particles smaller than an atom. Protons, neutrons and electrons are subatomic particles. In other words, they are particles that are smaller than the atom.

Symbol: Elements have been given a symbol. The symbol consists of one, two or three letters. If there is more than one letter for the symbol, only the first letter is capitalized. The symbols for some elements have been known since ancient times and are derived from their Latin names. Ex: Potassium (K) is Kalium in Latin. Sodium (Na) is Natrium in Latin.

Valence electrons are electrons outside filled rings or shells. They are the outer electrons.


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