Atoms and Molecules

This page will discuss the following:

1. Types of chemical bonds
2. Isomers
3. Formal Charge

1. Types of Chemical Bonds

Chemical bonds are the joining of two atoms that stabilize the energy of atoms

There are two types of chemical bonding applied in Organic Chemistry: Ionic and Covalent

Ionic Bonding	Covalent Bonding
1. requires full transfer of an electron 2. Attraction between charged ions 3. Forms a salt 4. Occurs between high electronegativity and low ionization energy elements Examples are: NaCl, AgCl, NaCN	1. Electrons are shared between atoms 2. “Discrete bonds” are created instead of crystal 3. Molecules are formed with distinct shape Examples are: Ethanol, Acetic Acid

2. Isomers

A molecular formula might have different structures and we call these molecules, isomers

Example:

(Will Add after Getting ChemDraw)

Constitutional Isomers are molecules with different connectivity of atoms while having the same molecular formula.

How does covalent bonding affect isomers?

Each element usually makes a determined number of covalent bonds. This is usually a function of valence electrons and their corresponding lone pairs.

Each atom has a unique number of valence electrons. If the atom has less than 4 valence electrons, the number of bonds equate to the number of valence electrons. If the atom has more than 5 valence electron, then number of bonds is 8 minus its corresponding valence electrons. Here’s a table of atoms that are commonly used in organic chemistry.

Atom	Number of Bonds
Hydrogen	1
Carbon	2
Nitrogen	3
Oxygen	4
Halogen	1

NOTE: SECOND PERIOD ELEMENTS CANNOT HAVE MORE THAN 8 VALENCE ELECTRONS

3. Formal Charge

What happens when an atom contains more or less bonds on that molecule? That molecule will be assigned a formal charge, assuming the electrons surrounding it are shared equally.

The formula for determining the formal charge is shown below:

Formal Charge = Number of Valence Electrons – (Number of Bonds + Number of Lone Pairs)

Number of Bonds = the number of “sticks” the atom has

Number of Lone Pairs = one lone pair counts as two

Another technique that I use is calculating the difference between how many electrons an atom should have and how many electrons it currently has.

(Examples will be provided here in the future)