Lesson 2 chemical bondings

Question 1

What is electronegativity?

Answer 1

the tendency of an atom or a functional group to attract electrons toward itself

Question 2

What does “δ+” mean?

Answer 2

The atom or the functional group has less electronegativity than the other atom or the functional group

Question 3

What does “δ-“ mean?

Answer 3

The atom or the functional group has more electronegativity than the other atom or the functional group

Question 4

How to identify whether they are polar or non-polar?

Answer 4

Polar bond has larger differences, which is larger than 0.4

Non-polar bond has no or less differences, which is equal or less than 0.4

Question 5

What are intramolecular bonds?

Answer 5

Bonds occur WITHIN molecules

Question 6

List out all types of intramolecular bonds.

Answer 6

Ionic
Covalent
Polar Covalent

Question 7

Explain ionic bond.

Answer 7

The electronegativity is more than 1.7
Electrons are TRANSFERRED from a metal atom to a nonmental atom

Question 8

Explain non-polar covalent bond.

Answer 8

The electronegativity is between 0 to 0.5
Electrons are EQUALLY SHARED between two non-metals

Question 9

Explain polar covalent bond.

Answer 9

The electronegativity is between 0.5 to 1.7
Electrons are UNEQUALLY SHARED between two non-metals
“Partially charged”

Question 10

What is the difference on time of covalent bond and polar covalent bond?
“Assume the differences of the electronegativity of the molecules are between 0.5 to 1.7”

Answer 10

Covalent bond: Elements equally shared electrons for SMALL % OF TIME
Polar covalent bond: Elements unequally shared electrons for LARGE % OF TIME

Question 11

How to determine a structure’s polarity?

Answer 11

Polarity of individual bonds
Shape of structure

Question 12

List of the properties of non-polar structures.
(Hint: The differences between individual bonds will slightly affect the properties.)

Answer 12

Individual bonds: non-polar
Structure: symmetrical
Example: Methane

Individual bonds: polar
Structure: symmetrical
Example: CO2
Because of the pulling force of polar bond, bonds “cancel” each other –> making them non-polar

Question 13

List of the properties of polar structures.

Answer 13

Individual bonds: polar
Structure: asymmetrical
Example: ammonia
Because it is asymmetrical, bonds DO NOT “cancel” each other –> making them polar

Question 14

What is intermolecular bonds?

Answer 14

Bonds occur BETWEEN molecules

Question 15

List out all types of Van Der Waals forces.

Answer 15

London forces (London dispersion forces)
Dipole-Dipole forces
Hydrogen bonds

Question 16

Explain London Forces.

Answer 16

The weakest forces among all the forces
Exist between ALL atoms and molecules
Formed from the temporary unequal distribution of electrons
–> due to the random motion around the nuclei of atoms
–> electrons constantly moving, form variation of distribution of electrons

Question 17

What role does London force perform between noble gases and non-polar molecules? Why is it important?

Answer 17

It performs a force of attraction between noble gases and non-polar molecules.
It is important because it is the only force of attraction.

Question 18

Why does the size of non-polar molecules matter?

Answer 18

Small non-polar molecules are gases due to the weak attraction (E.G. methane CH4)

Large non-polar molecules are liquid due to the cumulative effect (E.G. octane C8H18)

Question 19

Explain dipole-dipole forces.

Answer 19

Hold polar molecules to one another.

Question 20

How does dipole-dipole forces hole polar molecules or one another?

Answer 20

The slightly negative end of one molecule attracts to the slightly positive end of another molecules

Question 21

Explain hydrogen bonds.

Answer 21

The strongest among all the forces
Perform strong dipole-dipole forces

Question 22

Where does hydrogen bond happen the most?

Answer 22

It occurs between H in a polar molecule AND another electronegative N or O of a neighbouring polar molecule mostly.
It does bond with F, but not as much as N and O because there is not much F inside the body.

Question 23

What are the differences between London forces and dipole-dipole forces?

Answer 23

London forces exist between all atoms and molecules while dipole-dipole only exist in polar molecules