Covalent Bonding Notes

Ionic vs Covalent Bonding Ionic: electron(s) leave one atom & gained by another atom to satisfy both atoms’ octets, this results in the formation of ions. The resulting opposite charges attract each other. Covalent: electrons are shared by two or more atoms to satisfy their octets.

How can you tell if a bond is IONIC or COVALENT? Subtract the two electronegativity values >1.7 to 4.0: Ionic >0.4 to 1.7: Polar Covalent 0.0 to 0.4: Non-Polar Covalent Electronegativity: atom’s ability to attract electrons in a chemical bond. (higher electronegativity means the atom wants electrons more)

How can you tell if a bond is IONIC or COVALENT? Easy way: All metals = metallic bond Nonmetals and Metals = ionic bond All nonmetals = covalent bond

Yes, there are 2 kinds of covalent bonds! Polar covalent: the electrons are shared, but one atom is pulling on the electrons a lot more. The electrons spend more time around that atom. Nonpolar covalent: the electrons are evenly shared between the two atoms.

O(3.5) – H (2.1) = 1.4 Polar covalent bond

Properties of Covalent Compounds 1) Have much lower melting and boiling points than ionic compounds. 2) Covalent compounds are soft and squishy (compared to ionic compounds, anyway).

Properties, Cont’d 3) Covalent compounds tend to be more flammable than ionic compounds. – There are exceptions to this rule! 4) Do not conduct electricity in water. 5) Gases, liquids, or solids

The Convalent Bond The neutral particle is formed when atoms share electrons is called a molecule

Bond Dissociation Energy Bond dissociation energy = energy required to break a covalent bond. Highest bond energy Lowest bond energy Hardest to break Easiest to break TripleDoubleSingle BondBondBond Shortest bond length Longest bond length Strongest Weakest

Chemical Bonds Bond Type Single Double Triple # of e’s Notation — =  Bond order Bond strength Increases from Single to Triple Bond lengthDecreases from Single to Triple

How to Draw Covalent Molecules EXAMPLE : CF 4 1) Find the total number of electrons 2) Write the symbol for the single atom surrounded by all the other atoms – If there is not a single atom Use the first atom Use the most electronegative atom 3) Connect all the molecules by drawing a single bond (a line)

4) Subtract the number of electrons that are used from the total number of electrons 5) Distribute the remaining electrons so that all atoms satisfy the octet rule – *Remember when there is a line connecting elements it represents 2 electrons* Place Double and Triple bonds when necessary

Another Example Water

Another Example N 2

Exceptions and special situations – Hydrogen will only ever form a single bond and will never have lone pairs around it. – Boron can also have less than an octet because of the 3 valence electrons. – Only atoms in the 3rd row and beyond can break the octet.

How to Name Covalent Compounds 1. Name the first element (normal name) 2. Name the second element and change the ending to –ide 3. Add prefixes to indicate how many atoms of each element are in the molecule (Subscripts) Exception: no need to use “mono” for first element. Example: CO 2 = carbon dioxide

Prefixes Subscriptprefix 1Mono 2Di- 3Tri- 4Tetra- 5Penta- 6Hexa- 7Hepta- 8Octa- 9Nona- 10Deca-

Examples PH 3 CO N 2 O 3

Examples Dinitrogen Hexafluoride chlorine dioxide iodine pentafluoride

Diatomics Diatomic elements are elements that do not exist singularly in nature because they are highly reactive. “Which elements are the diatomics?” “HON, it’s the halogens!” H 2, O 2, N 2, F 2, Cl 2, Br 2, I 2