Bonding and Structure

Question 1

Define ionic bonding

Answer 1

Ionic bonding is the electrostatic attraction between positively and negatively charged ions.

Question 2

when construction dot cross diagrams what must be added to the products and why?

Answer 2

square brackets and charger to show that the charge is spread over each ion

Question 3

Why are only the outer shells shown in dot cross diagrams?

Answer 3

Only the outer shells are shown because the inner shells are not used in bonding

Question 4

explanation behind the structure of giant ionic lattices

Answer 4

Each ion attracts oppositely charged ions in all directions

Question 5

what arrangement are giant ionic lattices

Answer 5

regular arrangement.

Question 6

Why do ionic (lattice) compound have high melting/boiling points?

Answer 6

Large amounts of energy are required to overcome the strong electrostatic forces between oppositely charged ions.

Question 7

What two factors increase the melting and boiling points of ionic (lattice) compounds?

Answer 7

1. The charge of the ion, higher charge creates stronger electrostatic forces between ions and therefore higher melting and boiling points.
2. Size of the ions, the smaller the size of the ions the closer they are to one another, the stronger the electrostatic forces, the higher the melting and boiling points.

Question 8

what are most ionic compounds soluble in?

Answer 8

Polar solvents (water)

Question 9

What 2 processes occur for solubility to take place?

Answer 9

1. Solvent must break down the lattice.
2. Solvent must surround and attract each ion

Question 10

What factor effects solubility?

Answer 10

Charge of ions, higher the charge the lower the solubility, highly charged ion’s electrostatic forces are too strong for the solvent to break up, leading to low solubility.

Question 11

What states do ionic compounds conduct electricity?

Answer 11

Liquid an aqueous as the ions can then act as mobile charge carriers.

Question 12

Define covalent bonding

Answer 12

Covalent bonding is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.

Question 13

what occurs in double covalent bonding

Answer 13

Two pairs of electrons are shared between the bonding nuclei

Question 14

what occurs in triple covalent bonding

Answer 14

Three pairs of electrons are shared between the bonding nuclei

Question 15

Define dative/ coordinate bonding

Answer 15

Dative covalent bonding is a covalent bond in which the shared pair of electrons is supplied by one of the bonding atoms only.

Question 16

Define average bond enthalpy

Answer 16

Average bond enthalpy is a measure os covalent bond strength.

Question 17

Describe electronegativity

Answer 17

The attraction of a bonded atom for the pair of electrons in a covalent bond

Question 18

How is electronegativity measured

Answer 18

Pauling scale

Question 19

Electronegativity increases (periodic table)

Answer 19

Across the groups (left to right)
Up the period

Question 20

Describe non polar bonds

Answer 20

The electron pair is evenly shared between the bonded atoms.

Question 21

what must be the same for a non polar bond to occur

Answer 21

The bonded atoms must have the same electronegativity/ same element

Question 22

Describe polar bonds

Answer 22

The electronegativity of the bonded atoms are not the same, the electron pair is therefore shared unequally between the bonded atoms

Question 23

In a molecule what is the separation of opposite charges called

Answer 23

Dipole, resulting in a permanent dipole

Question 24

What makes a polar molecule

Answer 24

Overall dipole

Question 25

Why is CO2 not a permanent dipole

Answer 25

Both dipoles cancel each other out, (both horizontal with opposing directions)

Question 26

What are intermolecular forces?

Answer 26

weak interactions between the dipoles of different molecules

Question 27

Order the intermolecular forces in increasing bond strength

Answer 27

1.(London forces) Induced dipole-dipole
2. Permanent dipole-dipole interactions
3.Hydrogen bonding

Question 28

Describe induced dipole-dipole (London forces)

Answer 28

Weak intermolecular forces that exist between all molecules.

Question 29

Describe the formation of induced dipole-dipole moments

Answer 29

1) When electrons become unevenly distributed an instantaneous dipole will occur.
2) The instantaneous dipole then induces an instantaneous dipole in neighbouring molecules.
3) This produces a knock on effect inducing dipoles in further molecules.
4) Creating a weak interaction between the molecules.

Question 30

What increases the strength on induced dipole-dipole (London) forces

Answer 30

Larger numbers of electrons creates a stronger dipole, inducing stronger interactive forces between the molecules.

Question 31

Describe permanent dipole-dipole forces

Answer 31

The weak intermolecular forces between permanent dipoles in different molecules.

Question 32

Describe the melting and boiling points of simple molecular lattices

Answer 32

Low melting and boiling points

Question 33

Describe the solubility of simple molecular substances (non polar)

Answer 33

Soluble in non polar solvents, not soluble in polar solvents as the polar solvents intermolecular forces are too strong to break apart, not allowing them to weaken the intermolecular forces of the simple molecular lattice

Question 34

Describe the solubility of (polar) simple molecular substances

Answer 34

May be soluble in polar solvents

Question 35

What is the electrical conductivity of simple molecular substances

Answer 35

no conductivity as there are no mobile charge particles.

Question 36

Define hydrogen bonding

Answer 36

Intermolecular bonding between electronegative (lone pair carrying) atoms ‘Oxygen, Fluorine, Nitrogen’ and Hydrogen. Between the lone pairs of one electronegative atom of one molecule to the hydrogen atom from another molecule.

Question 37

Describe the melting and boiling points of water

Answer 37

High (compared to expected without hydrogen bonding).

Question 38

Describe the density of water in liquid and solid state

Answer 38

Water is less dense in its solid state as hydrogen bonding forces the water molecules to form a tetrahedral structure occupying more volume, making the solid less dense than the liquid form.