Question

Polar Covalent, Covalen or Ionic? What are each of their electronegative charges?

Q: My A:

1. ) K-O Ionic? 4.0(K)-2.0(O)= 2

2.) H-C Covalent 1.0(H)-1(C)=0

3.) S-C Covalent 3(S)-1(C)=2

4.) O-C Covalent 2(O)-1(C)=1

This is how I did it but its not correct as I am seeing in my textbook the numbers have decimals, for example:

NaCl 3.0 (Cl)-0.9(Na)=2.1 Ionic

Where does the 3.0 and 0.9 # come from? I though it was taking the period it was in and that representing the number as you can see in the breakdown above that is probably wrong.

Thank you!

Answer 1

They're asking you to indicate the type of bond in each compound, an empirical rule is based in the difference of electronegativities. The values indicated in your book refer to the Pauling electronegativity values, you can find them in some periodic tables or in general or inorganic chemistry books.

The differences are not a convention, so they may vary a little:

Difference of electronegativity:

0.0 - 0.5 ----> Non polar covalent bond

0.6 - 1-6 ----> Polar covalent bond

>2.0 ----> Ionic bonding

1) K-O : Electronegativity of K: 0.9 , electronegativity of O: 3.5

Diference of electronegativity: 3.5 - 0.9 = 2.6 ----> Ionic bond

2) H-C: Electronegativity of H: 2.1 , electronegativity of C: 2.5

Diference of electronegativity: 2.5 - 1.2 = 0.4 ----> Non polar covalent bond

3) S-C: Electronegativity of S: 2.5 , electronegativity of C: 2.5

Diference of electronegativity: 2.5 - 2.5 = 0 ----> Non polar covalent bond

4) O-C : Electronegativity of O: 3.5 , electronegativity of C: 2.5

Diference of electronegativity: 3.5 - 2.5 = 1 ----> Polar covalent bond