Understanding Covalent Bonds: Why Atoms Share Electrons

1. Covalent Bonds

2. Why do atoms bond? • Atoms want STABILITY- to achieve a 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

3. What is a covalent bond? • Covalent bond - the chemical bond that results from sharing of valence electrons • Occurs with elements close to each other on the periodic table • Between a nonmetal and a nonmetal • Molecule is two or more atoms bonded covalently

4. Examples of Molecules • F2 • H2O • NH3 (ammonia) • CH4 (methane) • Notice there are no metals, only non-metals

5. 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

6. 3 Types of Covalent Bonds: Single, Double and Triple bonds

7. Strength of Covalent Bond • Several factors control bond strength • Number of shared electrons-the more electrons shared, the shorter the bond, the greater the bond strength • Size of the atoms

8. Single Covalent Bonds • Each atom shares one pair (2 total) of electrons • Longest bond • Weakest bond of the three

9. Double Covalent Bonds • Each atom shares two pairs (4 total) of electrons • Medium length bond • Medium strength bond

10. Triple Covalent Bond • Each atom shares three pairs (total 6) of electrons • Shortest bond • Strongest bond • Carbon and nitrogen can form triple covalent bonds

11. Single, Double & Triple Bonds

12. Covalent Molecule Properties • 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