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Building Biomolecules
Concept 1: CHNOPS: The Six Most Abundant Elements of Life
   Practice (1 page)
   Review (1 page)
Concept 2: Valence and Covalent Bonding
Concept 3: Organic Molecules: Hydrocarbons
   Practice (1 page)
   Review (1 page)
Concept 4: Isomers
   Review (3 pages)
Concept 5: Polarity
   Review (2 pages)
Concept 6: The Functional Groups
   Practice (2 pages)
   Review (5 pages)
Concept 2: Valence and Covalent Bonding
Each element has a characteristic valence that determines the number of covalent bonds it can form.
The ability of an atom to combine with other atoms depends on the number of electrons in the outer shells of the atoms. Some elements, the so-called noble gases, have complete outer shells and do not share electrons. Many elements will share electrons with other elements, such that each element completes its outer electron shell capacity.

A shared electron pair is called a covalent bond. The number of covalent bonds that each element can form is called its valence.
Spheres (6) with valence positions
The CHNOPS atoms are shown above. Each valence position is represented by a stick protruding from the atom.