Bonding

Question 1

ionic bonding definition

Answer 1

involves electrostatic attraction between oppositely charged ions in a lattice

Question 2

what is a covalent bond?

Answer 2

the electrostatic attraction between 2 nuclei and a shared pair of electrons between them
- can be single, double or triple
- represented by a line

Question 3

what is a dative/co-ordinate covalent bond?

Answer 3

a shared pair of electrons with both electrons supplied by one atom
- represented by an arrow

Question 4

what is metallic bonding?

Answer 4

attraction between delocalised electrons and positive ions arranged in a lattice

Question 5

common compounds/elements and their charges (+)

Answer 5

1+ charge
- Cu
- Ag
- NH4

2+ charge
- Pb (II)
- Fe (II)
- Cu (II)

3+ charge
- Cr (III)
- Fe (III)

Question 6

common compounds and their charges (-)

Answer 6

1- charge
- NO3
- OH
- HCO3

2- charge
- CO3
- SO4
- SO3

3- charge
- PO4

Question 7

what are the four types of crystal structure?

Answer 7

• ionic eg. sodium chloride
• metallic eg. magnesium
• macromolecular (giant covalent) eg. diamond, graphite
• simple molecular eg. ice, iodine

Question 8

Macromolecular/giant covalent

Answer 8

• high mp/bp=lots of strong covalent bonds=lots of energy to break
• insoluble
• can conduct if they have delocalised e-
• solids

Question 9

Metallic

Answer 9

• high mp/bp=strong electrostatic forces bw +ve ions and delocalised e-
• insoluble
• can conduct electricity+heat due to delocalised e-
• shiny metal

Question 10

Ionic

Answer 10

• high mp/bp=giant ionic lattice w/ strong electrostatic forces bw oppositely charged ions
• (mostly) soluble
• can conduct charge when molten but not as solids
• crystalline solids

Question 11

what is electronegativity?

Answer 11

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

Question 12

how do we measure electronegativity?

Answer 12

Pauling scale
goes from 0 to 4
F being the most electronegative element

Question 13

factors affecting electronegativity

Answer 13

• nuclear charge - more protons=stronger attraction between nucleus+bonding pair of electrons
• ↓ atomic radius=closer to nucleus=stronger attraction between nucleus and bonding pair of electrons
• shielding - less shells of electrons between nucleus and electrons=less shielding/repulsion=stronger attraction between nucleus and bonding pair of electrons

Question 14

electronegativity trend going down a group

Answer 14

it decreases
- ↑ atomic radius
- more shielding
- ∴ ↓ attraction between nucleus and bonding pair of electrons

Question 15

electronegativity trend going across a period

Answer 15

it increases
- ↓ atomic radius
- ↑ nuclear charge
- shielding remains the same
- ∴ ↑ attraction between nucleus and bonding pair of electrons

Question 16

how is the distribution of electrons between elements with diff electronegativities

Answer 16

unsymmetrical=a polar covalent bond+ can cause a molecule to have a permanent dipole

Question 17

relationship between electronegativity and bond polarity

Answer 17

the greater the electronegativity difference, the greater is the bond polarity

Question 18

how can polarisation be measured?

Answer 18

dipole moments

Question 19

what are intermolecular forces?

Answer 19

forces of attraction that exist between all simple covalent molecules

Question 20

types of intermolecular forces

Answer 20

• induced dipole–dipole (van der Waals, dispersion,
  London) forces
• permanent dipole–dipole forces
• hydrogen bonding

Question 21

how do van der Waals form?

Answer 21

• electrons orbit around atom/molecule=fluctuations in electron density=form temporary/instantaneous dipole=induce as a dipole in a neighbouring molecule/atom=weak force of attraction between the 2 molecules

Question 22

factors affecting van der Waals forces

Answer 22

• more electrons=stronger van der Waals forces=greater chance of asymmetry=more frequent formation of temporary dipoles

Question 23

predict the electronegativity of group 7

Answer 23

• group 7=halogens have van der Waals forces between molecules
• as you go down the group=↑atomic radius+↑shielding= therefore ↓electronegativity

Question 23

what affects the shape of a molecule?

Answer 23

• electron pairs=as far apart as possible=minimise repulsion
• lone pair–lone pair repulsion>lone pair–bond pair repulsion>bond pair–bond pair repulsion

Question 24

shape of molecules (total no. of electrons pairs=2)

Answer 24

* 2 bonding pairs+0 lone pairs= linear, 180°

Question 25

shape of molecules (total no. of electrons pairs=3)

Answer 25

* 3 bonding pairs+0 lone pairs= trigonal planar, 120° * 2 bonding pairs+1 lone pair=bent (v-shape), 118°

Question 26

shape of molecules (total no. of electrons pairs=4)

Answer 26

* 4 bonding pairs+0 lone pairs=tetrahedral, 109.5° * 3 bonding pairs+1 lone pair=trigonal pyramidal, 107° * 2 bonding pairs+2 lone pairs=bent (v-shape), 104.5°

Question 27

shape of molecules (total no. of electrons pairs=5)

Answer 27

* 5 bonding pairs+0 lone pairs=trigonal bipyramidal, 90° and 120° * 4 bonding pairs+1 lone pair=trigonal pyramidal/see-saw, 89° and 119° * 3 bonding pairs+2 lone pairs=trigonal planar or t-shape, 120° or 89°

Question 28

shape of molecules (total no. of electrons pairs=6)

Answer 28

* 6 bonding pairs+0 lone pairs= octahedral, 90° * 5 bonding pairs+1lone pair=sqaure pyramid, 89° * 4 bonding pairs+2 lone pairs=sqaure planar, 90°

Question 29

Simple covalent/ molecular

Answer 29

* low mp/bp=weak intermolecular (vdW, H-bonds) forces bw molecules * (mostly) insoluble * x conduct=fixed/localised e- + x ions * gases+liquids

Question 30

How do H-bonds form?

Answer 30

For hydrogen bonding to take place the following is needed: A species which has an O, N or F (very electronegative) atom bonded to a hydrogen When hydrogen is covalently bonded to an O, N or F, the bond becomes highly polarised The H becomes so δ+ charged that it can form a bond with the lone pair of an O, N or F atom in another molecule For example, in water

Question 31

How do permanent dipole-dipole forces form?

Answer 31

Polar molecules have permanent dipoles The molecule will always have a negatively and positively charged end Forces between two molecules that have permanent dipoles are called permanent dipole - dipole forces The δ+ end of the dipole in one molecule and the δ- end of the dipole in a neighbouring molecule are attracted towards each other