Bonding

Question 1

What is an ionic bond?

Answer 1

An ionic bond is the electrostatic force of attraction between a positively charged ion and a negatively charged ion formed by electron transfer.

Question 2

What is a covalent bond?

Answer 2

A covalent bond is the electrostatic force of attraction between a shared pair of electrons and their nuclei.

Question 3

Why do ionic compounds have such high melting/boiling points?

Answer 3

Ionic compounds contain strong ionic bonds and is arranged in a lattice of positive and negative ions which requires lots of energy to overcome and hence has a high melting/boiling point.

Question 4

Why is the melting point of MgO higher than that of NaCl?

Answer 4

The melting points are smaller when the ions are smaller (smaller atomic radius) or have higher charges.

Question 5

What is Dative Covalent Bonding/Co-ordinate Bonding?

Answer 5

A dative covalent bond forms when the shared pair of electrons in the covalent bond come from only one of the bonding atoms.

Question 6

What is Metallic bonding?

Answer 6

The electrostatic attraction between positive metal ions and negative delocalised electrons. ‘Positive metal ions in a sea of delocalised electrons’

Question 7

When and why do Ionic compounds conduct electricity?

Answer 7

Ionic compounds conduct electricity when molten or aqueous as the ions can move freely and carry a charge.

Question 8

What are the properties of ionic compounds and why?

Answer 8

They are brittle as when the layers slide over each other the ions line up with like charge ions and repel.

Ionic compounds conduct electricity when molten or aqueous as the ions can move freely and carry a charge.

Question 9

What are the properties of Metallically bonded compounds?

Answer 9

They can conduct electricity as they have delocalised electrons which are free to move and carry a charge.

They are ductile and malleable as the layers can slide over each other without repelling and so can be drawn into wires or into other shapes.

Question 10

What 3 factors effect the strength of a metallic bond?

Answer 10

1. The number of protons/The strength of the nuclear attraction
2. The size of the ion (The smaller the ion the greater stronger the bond)
3. The number of delocalised electrons (The more delocalised electrons the stronger the bond)

Question 11

What are the 5 ways to explain shape of a compound?

Answer 11

1. State number of bonding pairs and lone pairs of electrons.
2. State that electron pairs repel and try to get as far apart as possible
3. If there are no lone pairs state that the electron pairs repel equally.
4. If there are lone pairs of electrons, then state that lone pairs repel more than bonding pairs.
5. State the actual shape and bond angle.

Question 12

In what order do the following have the greatest repulsion from greatest to weakest: Bond-Bond, Lone-Lone and Lone-Bond?

Answer 12

Lone-Lone>Bond-Lone>Bond-Bond

Question 13

What is electronegativity?

Answer 13

Electronegativity is the relative tendency of an atom to form a covalent bond in a molecule to attract electrons in a covalent bond to itself.

Question 14

What are the 3 factors which effect electronegativity?

Answer 14

1. The proton number (as proton number increases so does electronegativity).
2. The atomic radius (as the atomic radius decreases the electronegativity increases).
3. As the amount of shielding increases the electronegativity decreases.

Question 15

What is the most electronegative element?

Answer 15

Fluorine

Question 16

What difference on the Pauling scale creates an ionic bond?

Answer 16

1.9+

Question 17

What difference on the Pauling scale creates a polar covalent bond?

Answer 17

0.4-1.8

Question 18

What difference on the Pauling scale creates a non-polar covalent bond?

Answer 18

0.0-0.4

Question 19

What is a polar covalent bond?

Answer 19

A polar covalent bond has an unequal distribution of electrons in the bond and produces a charge separation.

Question 20

When is a molecule polar?

Answer 20

A molecule is polar when all of the electronegativities are pulling equally around a central atom and has a net 0

Question 21

When is a covalent bond polar?

Answer 21

A bond is polar when the difference in electronegativity is between 0.4-1.8.

Question 22

What are the three types of intermolecular forces?

Answer 22

1. Van der Waals forces (induced dipole)
2. Permanent dipole-dipole
3. Hydrogen bonding

Question 23

What intermolecular forces are the strongest in order?

Answer 23

1. Hydrogen bonding
2. Permanent dipole dipole
3. Van der Waals forces

Question 24

Why do the boiling points of halogens increase down the group?

Answer 24

As proton number increases the number of electrons increases and so does the size of the molecules. This creates greater Van der Waals forces and so requires more energy to overcome those intermolecular forces.

Question 25

Why do branch chain alkanes have lower boiling points than straight chain alkanes?

Answer 25

They have a larger surface area and their shape is slightly irregular and so cannot tessellate well enough so the Van der Waals forces aren’t as strong as they could be.

Question 26

What are the only three elements which can form hydrogen bonds?

Answer 26

Nitrogen, Oxygen and Fluorine

Question 27

Explain the boiling points of H2O, H2S, H2Se and H2Te?

Answer 27

As the elements move down the group, their atomic number increases and so they have greater Van der Waals forces and so require more energy to overcome those forces. Water is the exception however as it contains hydrogen bonds which require more energy to overcome than any of the intermolecular forces.

Question 28

When do hydrogen bonds form?

Answer 28

A hydrogen atom is bonded to a very electronegative atom will produce a strong partial positive charge and will have a lone pair of electrons and so will have hydrogen atoms attracted to the N/O/F atoms.

Question 29

How do Van der Waals forces work?

Answer 29

The distribution of charge in a molecule is always changing and if at one point the electrons all move to one side it will form a dipole and cause a chain reaction to other like molecules. The larger the molecule, the greater the strength of the Van der Waals forces.

Question 30

What should you look out for when drawing hydrogen bonds?

Answer 30

1. Show all lone pairs 2. Show all dipoles and all partial charges 3. Show hydrogen bond from lone pair to hydrogen atom

Question 31

Linear

Answer 31

180 degrees 2 bond pairs 0 lone pairs

Question 32

Trigonal planar

Answer 32

120 degrees 3 bond pairs 0 lone pairs

Question 33

Tetrahedral

Answer 33

109.5 degrees 4 bonding pairs 0 lone pairs

Question 34

Trigonal pyramidal

Answer 34

107 degrees 3 bonding pairs 1 lone pair

Question 35

Trigonal Bipyramidal

Answer 35

90 degrees and 120 degrees 5 bonding pairs 0 lone pairs

Question 36

See-Saw

Answer 36

119 and 89 degrees 4 bonding pairs 1 lone pair

Question 37

Trigonal Planar/T-shape

Answer 37

120 degrees 3 bonding pairs 2 lone pairs (opposite each other)

Question 38

Octahedral

Answer 38

90 degrees 6 bonding pairs 0 lone pairs

Question 39

Square planar

Answer 39

90 degrees 4 bonding pairs 2 lone pairs

Question 40

Square Pyramidal

Answer 40

89 degrees 5 bonding pairs 1 lone pair

Question 41

Why is ice less dense than water?

Answer 41

The hydrogen bonding holds the water molecules away from each other.

Question 42

Bent

Answer 42

118 degrees 2 bonding 1 lone

Question 43

Bent 2 lone

Answer 43

104.5 degrees 2 bonding 2 lone