covalent bonds why do atoms bond? atoms want noble gas configuration (octet) for ionic bonds there...

Covalent Bonds

Why do atoms bond?

• Atoms want noble gas configuration (octet)• For ionic bonds there is a transfer of electrons

to get an octet of electrons• For covalent bonds there is a sharing of

electrons to get an octet

What is a covalent bond?

• Covalent bond - is the chemical bond that results from sharing of valence electrons– Occurs with elements close to each other on the

periodic table– Ex: H2O

– Between a nonmetal and a nonmetal– Molecule is two or more atoms bonded covalently

Examples of Molecules

• F2

• H2O

• NH3 (ammonia)

• CH4 (methane)

• Notice there are no metals, only non-metals

Diatomic molecules

• Some atoms do not exist as a single atom• Atoms that exist as two

H2, O2, N2, Cl2, Br2, I2, F2

• HONClBrIF• Magnificent 7-don’t forget H

3 Types of Covalent Bonds

• Single Covalent Bond• Double Covalent Bond• Triple Covalent Bond

3 Pencil Demo for Single, Double and Triple Covent bonds

• Make as many observations as you cani.e. facial expressions, body position, muscles

used, noises made, force or energy exerted, etc.

Single Covalent Bonds

• Each atom shares one pair of electrons• Each atom shares 2 electrons• Longest bond• Weakest bond of the three

Double Covalent Bonds

• In a double bond, each atom shares two pairs of electrons

• Each atom shares 4 electrons• Medium length bond• Medium strength bond

Triple Covalent Bond

• In a triple covalent bond, each atom shares three pairs of electrons

• Each atom shares 6 electrons• The shortest bond• The strongest bond• Carbon, nitrogen, oxygen, and sulfur can form

double and triple covalent bonds

Covalent Molecule Properties• Covalent molecular solids tend to be soft

solids, liquids, or gases at room temperature• Low melting and boiling points• Poor conductors of heat and electricity• Non-electrolytes – do not conduct electricity

in water

Strength of Covalent Bond

• Several factors control bond strength—Number of shared electrons-the more

electrons shared, greater the bond—Size of the atom—Bond length – the greater the bond length,

the weaker the bond