Bonding and Structure

Question 1

What is an ionic bond?

Answer 1

The electrostatic force of attraction between positively and negatively charged ions.

Question 2

What are the properties of ionic compunds?

Answer 2

1.Can’t conduct electricity when solid as the strong ionic bonds hold the charges in place. When molten or aqeous the delocalised electrons are free to move so ionic compounds can conduct electricity.
2.High melting and boiling point due to strong electrostatic forces of reaction
3.Regular structure
4.Giant repeating structure
4.Dissolve in water (polar)

Question 3

What is a covalent bond?

Answer 3

The electrostatic forces of attraction between two neuclei of two atoms and the shared electrons.

Question 4

What is a dative covalent or coordinate bond?

Answer 4

Where one atom donates 2 electrons to an atom or ion for form a bond. An example is Nitrogen in ammonium (NH4+). H+ is electron deficient, so has space foe 2 e- in its shell which are provided by Nitrogen.

Question 5

Why do molecules have specific shapes with specific angles?

Answer 5

Because the bonds repel each other equally. Bonds contain electrons which want to be as far apart as possible

Question 6

Why do lone pairs repel each other more than bonded pairs?

Answer 6

Because bonded pairs are further away from the nucleus due to being in a bond with another atom. Lone pairs only exist around one atom so are closer and repel each other more. This repulsion gives rise to different shapes.

Question 7

How to determine shape of a molecule?

Answer 7

Number of bonded and lone pairs

Question 8

What is the shape of an atom with one bond and no lone pairs?

Answer 8

Linear
HCL

Question 9

2 bonds no lone pairs

Answer 9

Linear, 180 degrees
eg CO2

Question 10

2 bonds 2 lone pairs

Answer 10

Bent.
104.5 degrees3
eg H20

Question 11

3 bond pairs 0 lone pairs

Answer 11

Trigonal Planar
120 degrees
BH3

Question 12

3 bonded pair one lone pair

Answer 12

Pyramidal
107 degrees
NH3

Question 13

4 bonded pairs no lone pairs

Answer 13

Tetrahedral
109.5 degrees

Question 14

5 bond pairs 0 lone pairs

Answer 14

trigonal bipyramidal
90 and 180 degrees

Question 15

6 bond pairs 0 lone pairs

Answer 15

Octahedral
90 degrees

Question 16

What is electronegativity?

Answer 16

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

(They spend more time around the more electronegative atom, making it slightly more negative).

Question 17

How does electronegativity increase along the periodic table?

Answer 17

It increases the further right and up you go

Question 18

What is the most electronegative element and elements?

Answer 18

Flourine, Oxygen, Chlorine

Question 19

What is a polar bond?

Answer 19

The uneven distribution of electrons in a bond due to difference in electronegativity.

Question 20

What is a dipole?

Answer 20

The difference in charges of atoms in a molecule due to bond polarity.

Question 21

How can you get polar bonds but a non-polar molecule?

Answer 21

The polar bonds are symmetrical so cancel each other out, so the whole molecule has no overall polarity.

Question 22

What is a permanent dipole-dipole interaction?

Answer 22

When the permanent dipole of one molecule interacts with the permanent dipole of another molecule.
Eg water molecules interacting.

Question 23

What is an instantaneous dipole?

Answer 23

The moment where there is a difference in charge of atoms in a bond due to the random movement and distribution of electrons within that bond.

Question 24

What is an induced dipole?

Answer 24

A type of intermolecular force where one dipole interacts with another molecule, inducing a dipole in it.

Question 25

What are induced dipoles and permanent dipole-dipole interactions also known as?

Answer 25

Vander Waal forces.

Question 26

What does the strength of permanent dipoles depend on?

Answer 26

The difference in electronegativity of the atoms in the molecule. A larger difference = stronger charges and greater attraction.

Question 27

What does the strength of induced dipoles depend on?

Answer 27

The number of electrons in the bond of the molecules.
Eg Hydrogen only has 2 e- in its atom whereas each oxygen atom has 8 e- so makes weaker interactions.
So oxygen will have a higher melting and boiling point as more energy is requried to break the induced dipole dipole bonds than in hydrogen.

Question 28

What is a hydrogen bond?

Answer 28

Ozygen and hydrogen
Floruine and hydrogem

Question 29

What are the properties of water?

Answer 29

Ice is less dense than water as H bonds hold the molecules further apart in tetrahedral lattice structure. So it floats on water.

Question 30

Do simple covalent molecules conduct electricity?

Answer 30

No because they don’t contain any free moving charged particles.

Question 31

Why does iodine have a low boiling point?

Answer 31

It is a non-polar molecule so the only Van der Waal forces in its lattice are induced dipole-dipole interactions which are the weakest intermolecular force.
So, it tends to sublime at temperatures approaching 114 degrees.
A purple vapour is observed when iodine sublimes