6.2 - Electronegativity and polarity

Question 1

What is electronegativity?

Answer 1

The ability of an atom to attract the bonding electrons in a covalent bond

Question 2

How does electronegativity increase according to the elements in the periodic table?

Answer 2

• increases up
• increases across

Question 3

What are the three factors that affect electronegativity?

Answer 3

1. Nuclear charge
2. Atomic radius
3. Electron shielding

Question 4

How does nuclear charge affect electronegativity?

Answer 4

• Moving left to right across a period means that the number of protons in the nucleus increases
• This increased positive charge increases the attraction between the nucleus and the pair of electrons in the covalent bond, and therefore are more electronegative

Question 5

How does electron shielding affect electronegativity?

Answer 5

• As you go down periods the number of shells increases
• Electrons in the inner shells shield electrons in the outer shell from the positive charge of the nucleus
• Therefore the greater number of inner shells, the lower the electronegativity

Question 5

How does atomic radius affect electronegativity?

Answer 5

• Moving left to right across a period means that atomic radius decreases
• The smaller the atomic radius, the closer the bonding electrons will be to the nucleus of an atom, and therefore are more electronegative

Question 6

What is a pure covalent bond?

Answer 6

A non-polar bond where the bonded electron pair is equally shared between the bonded atoms
- occurs when the bonded atoms are the same or have the same/similar electronegativity

Question 7

What is a polar covalent bond?

Answer 7

A polar bond where the bonded electron pair is shared unequally between the bonded atoms
- occurs when the bonded atoms are different and have different electronegativity values

Question 8

What is a permanent dipole?

Answer 8

A dipole in a covalent bond that does not change

Question 8

What is a dipole?

Answer 8

A separation in electrical charge so that one atom of a polar covalent bond / polar molecule has a small positive charge and the other has a small negative charge

Question 9

When do permanent dipoles cancel each other out, resulting in an overall dipole of zero? e.g. o=c=o

Answer 9

• When the dipoles act in opposite directions and exactly oppose one another + unsymmetrical