Question

For each of the following, predict the bond type (pure covalent, polar covalent, or ionic) using the two criteria for predicting bond type.
a) CF4 b) At2 c) CsCl d) BaF2 e) PBr3

Answer 1

I would recommend looking at this

this website explains electronegativity fairly well
http://www.green-planet-solar-energy.com/electronegativity-values.html

But to sum it up essentially electronegative is the affinity an atom has for electrons, this property has a visible trend in the periodic table, which you should probably remember (if you want to understand why this trend is see the website I linked).
http://www.green-planet-solar-energy.com/images/PT-small-electroneg.gif

Note as you get redder the elements are more electronegative (note the numbers are alright guides but they are abstract and based purely on experimental method).

Answer 2

As a general rule:
-assume all group 13 to 17 atoms bonded to each other form covalent bonds
for example:
CO4, NF3
Note the exception with hydrogen forming covalent bonds CH4, H2O

-Bonds between group 1 (excludng hydrogen which forms covalent bonds look at its electronegativity) and 2 and group 13 to 17 atoms form ionic bonds, it is essentially where an element with high electronegativity just up and takes the electron from another element with very low electronegativity.
for example:
NaCl, Ca(OH)2

Polar covalent bonds - are essentially an uneven sharing of electrons (where the electrons in the bond stay around the more electronegative element) this occurs when one element bonded covalently to another element have a difference in electronegativity

For example: H2O

http://academic.brooklyn.cuny.edu/biology/bio4fv/page/image15.gif

Since oxygen has a greater electronegativity than oxygen you can see that the electrons will hang out more around the oxygen this will cause a partial positive charge on the hydrogen and a partial negative charge on the oxygen

Pure covalent bonds (also called non-polar bonds) - are when two atoms with the same electronegativity are bonded to each other and there is an even sharing of electrons (electrons hang out around both atoms an equal amount), this usually occurs when two of the same type of atoms are bonded to each other.

For example, N2, O2, F2 etc

A good image to describe bonds is here:

https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcQix4kyo4n726wmR1o1sP5y2FzOuD6fJwokmCGJyhsN02HQVFQH

Answer 3

That should be everything you need to answer this question

Answer 4

Thank you for all the help