(Green) Bond polarity

Question 1

what does it mean if the electron cloud is non-polar

Answer 1

it has a symetrical electron cloud

Question 2

what is a polar covalent bond

Answer 2

The result is a polar covalent bond. This is a covalent bond where the bonding pair of electrons are not shared equally by the two atoms in the bond.

Question 3

the uneven electron causes the molecule to be polar it now has two ______

Answer 3

positive/ negative electric poles

Question 4

what is the definition of electronegativity

Answer 4

The electronegativity of an atom is a measure of its ability to attract the shared pair of electrons in a covalent bond. It is a comparative scale based on Fluorine = 4.0

Question 5

describe the general trend in electronegativity in the periodic table

Answer 5

the electronegativity generaly increases as you go up and to the right

Question 6

How does electronegativity change i) across a period L eft to Right ?

Explain your answer

Answer 6

increases.

Proton number increases but completed inner shells / shielding remains constant. Atomic radius decreases and attraction for shared pair of electrons increases.

Question 7

How does electronegativity change down a group?

Explain your answer

Answer 7

decreases.

There is an extra completed inner shell which results in increased shielding, this and the increase in atomic radius outweigh the increase in proton number

Question 8

list these chemicals in electro negativity order
C
O
H
Cl
F
Br
N

Answer 8

F>O>N>Cl>Br>C similar to H

Question 9

what is the definition of electronegative

Answer 9

electronegative The bonds have a slightly positive pole d+ at one end and a negative one d-at the other.

Question 10

what is the seperation of charge called

Answer 10

dipole moment

Question 11

infocard (read and recite)

Answer 11

The theoretical dipole moment can be calculated from the amount of charge separation multiplied by the distance between the centres of charge.

Dipoles tend to line up in an electric field:-

Question 12

how can you tell if a compound is more ionic or covalent through electronegativity

Answer 12

the greater the diffrence in electronegativity the greater it is ionic and vice versa

CS = 0.7
F = 4.0

diffrence = 4 - 0.7 = 3.3 thefore it is more ionic

Question 13

Is it possible to have a purely covalent bond?

Explain why

Answer 13

Yes

Identical atoms will have identical electronegativities so the electron pair will be shared evenly

Question 14

Is it possible to have a purely ionic bond? Explain

Answer 14

no

even FrF is only 98% ionic.

The process of electrostatic attraction distorts the electron cloud.

Question 15

If a molecule is composed of just two atoms of different electronegativity then the MOLECULE AS A WHOLE IS POLAR.

Describe why the electron cloud is distorted in these molecules

Answer 15

Two atoms with different electronegativities, the more electronegative one attracts the shared pair of electrons more. This results in a distorted electron cloud, and the molecule now has a d+ and d- side so the bond and molecule are polar

Question 16

info card (read and recite)

Answer 16

In molecules with more than one covalent bond, if the molecule is symmetrical (state the shape as well in an answer) the bond polarities may cancel to leave a molecule with no dipole moment. The molecule will have a symmetrical electron cloud and be non-polar.

Question 17

what is a practical inoder to test for a polar molecule

Answer 17

Charge up a ruler, plastic rod or ballpoint pen case, by rubbing it on a piece of wool or synthetic material.

· Bring the charged rod close to a stream of water emerging from a burette jet. Do not let the rod become wetted.

What happens? Jet is attracted

· Repeat with the other liquids in the table.

Question 18

do questions from the pack