1. 2.3 Chemical Bonding and Electronegativity

2. Electronegativity and the Polarity of Bonds
When atoms bond together they share electrons
If atoms are identical, like H2, electrons are shared equally
If atoms are different, as in HCl, the attractions usually are not equal
One of the nuclei attracts the electrons more strongly than the other

3. Recall...
Electronegativity: a measure of the tendency of an atom to attract a bonding pair of electrons
Linus Pauling helped build the concept of electronegativity in 1922
The atom that is greater at keeping the electrons is said to be more electronegative and is indicated by δ- (Greek lowercase symbol for delta)
The other less electronegative atom is indicated by δ+

4. Periodic Table
Electronegativity values can be found on the periodic table
They are generally found underneath the atomic number

5. What is the electronegativty value (EN) for sodium?
What is the electronegativty value (EN) for tin?
What is the electronegativty value (EN) for francium?

6. Electronegativity Difference
To calculate the END take the absolute value of the difference between two bonded atoms
Ex: Cesium bromide
the difference between these values is 2.2
The greater the difference the more polar the bond.
-The smaller the difference the bond is more nonpolar.

7. Ionic Bonds (VERY POLAR)
have an electronegativity difference (∆EN) that is greater than 1.7
In polar bonds electrons are not shared equally and as a result one end of the bond becomes negative and the other becomes positive
These bonds usually form between non-metals and metals

8. Polar Covalent Bond an electronegativity difference (∆EN) below1.7
Can be classified as more non-polar than polar
Often occurs between non-metals, but can happen between metals and non-metals as well

9. Polar Covalent Bonds
Polar covalent bonds share electrons somewhat unequally
Have an electronegativity difference (∆EN) between 0 and 1.7

10. Non-polar covalent bonds (covalent bonds)
an electronegativity difference of 0
Non-polar bonds share electrons equally

11. Summary