Chapter 3.6 - Electronegativity, Bond Polarity In Covalent Bonds

Question 1

Define electronegativity

Answer 1

Electronegativity is the ability of an atom to attract a pair of electrons in a covalent bond.

Question 2

What does electronegativity depend on ?

Answer 2

• Nuclear charge
• The distance between the nucleus and the outer shell electrons
• the shielding of the nuclear charge by electrons in inner shell

Question 3

Trends in electronegativity

• Across a period
• Going up the group

Answer 3

Across a period

• Electronegativity increases ,
• The nuclear charge increases,
• shielding remains the same

Going up a group

• Electronegativity increases,
• there is less shielding present by inner shells,
• distance between nucleus and outer electrons increase

Question 4

Define polarity

Answer 4

• Polarity is about the unequal sharing of the electrons between atoms that are bonded together covalently,
• It is a property of the bond
• elements with different electro negativities

Question 5

Covalent bonds between 2 atoms that are the same :

Answer 5

When both atoms are the same

• they have the same electronegativity
• electrons in the bond must be shared equally
• bond is said to be non polar
• no charges

Question 6

Covalent bonds between two atoms that are different :

Answer 6

• different electronegativity
• electrons in the bond are not shared equally
• the electrons will be attracted towards the more electronegative element making it partially negative and leaving the other partially positive
• bonds like this are said to be polar, greater the difference in electronegativity the more polar is the covalent bond

Question 7

How does electronegativity affect polar bonding ?

Answer 7

The bigger the difference in electronegativity the more polar the bond is
The more electronegative element becomes partially negative

Question 8

Explain, in terms of electronegativity, why the boiling point of H2S2 is lower than H2O2

Answer 8

• Electro negativity difference less between H and S,

- weak van der waals forces between H2S2 molecules

Question 9

State the meaning of the term electronegativity

Answer 9

The ability of an atom to attract a pair of electrons towards itself in a covalent bond

Question 10

Suggest why the electronegativity of the elements increases from lithium to fluorine.

Answer 10

• nuclear charge increases across a period,

- shielding stays the same

Question 11

Deduce why the bonding in nitrogen oxide is covalent rather than ionic.

Answer 11

Small electronegativity difference

Question 12

Describe and explain non polar bonds

Answer 12

• if the 2 bonding atoms are identical, their attraction for the shared pair of electrons is equal bcoz they have equal value of electronegative,
• electrons are equally distributed between the bonding atoms ,
• bond is covalent

Question 13

Describe and explain polar bonds

Answer 13

• if the 2 bonding atoms made different, their attraction for the shared pair of electrons is unequal,
• the bonding atom with a greater attraction for the shared pair of electrons is more electronegative,
• bond is polarized

Question 14

Explain why some molecules with polar bonds do not have permanent dipole

Answer 14

• the symmetry of the molecule means that the effect of any permanent dipoles is cancelled out
• linear, Trigonal planar or tetrahedral shape, all atoms attached to the central atom are identical,
• no difference in charge exists across the molecule,
• molecule is non polar