2. bonding and structure

Question 1

what is an ion

Answer 1

a positively or negatively charged atom

Question 2

how are ions formed

Answer 2

when electrons are transferred from one atom to another

Question 3

what is a positively charged ion called

Answer 3

cation

Question 4

what is a negatively charged ion called

Answer 4

anion

Question 5

what is an ionic bond

Answer 5

the strong electrostatic forces of attraction between positive and negative ions

Question 6

how does ionic charge affect bonding

Answer 6

the greater the charge of an ion the stronger the bond. therefore higher melting and boiling points

Question 7

how does ionic radii affect bonding

Answer 7

smaller ions can pack closer together so have stronger ionic bonds as electrostatic attraction weakens with distance

Question 8

what does the size of an ion depend on

Answer 8

electron shells and atomic number
- ionic radii increases down the group because the atomic number increases and electron shells are added

Question 9

what is an isoelectronic ion

Answer 9

ions with the same number of electrons

Question 10

what happens to ionic radii of isoelectronic ions

Answer 10

it decreases as the atomic number increases as the number of protons increases so the attraction to the nucleus is greater

Question 11

physical properties of ionic compounds

Answer 11

• high melting points
• soluble in water but not non-polar solvents
• dont conduct when solid but do when molten or dissolves
  -cant be shaped

Question 12

how does migration of ions prove charged particles (experiment)

Answer 12

when you electrolyse copper chromate solution on wet filter paper the paper turns blue at the cathode and yellow at the anode. when a current is passed through a solution it causes positive ions to move to the cathode and negative ions to move to the anode

Question 13

what is a covalent bond

Answer 13

the strong electrostatic force of attraction between the two positive nuclei and the shared electrons in the bond

Question 14

how is bond enthalpy related to bond length

Answer 14

higher the electron density = stronger the attraction
higher the bond enthalpy = shorter the bond

Question 15

what is bond length

Answer 15

the distance between two nuclei where attractive and repulsive forces balance

Question 16

what is a dative covalent bond

Answer 16

both electrons come from one atom

Question 17

what is a bonding pair

Answer 17

pairs of electrons are shared with another atom in a covalent bond

Question 18

what is a lone pair

Answer 18

pairs of electrons that are not shared

Question 19

what repels more lone pairs or bonding pairs

Answer 19

lone pairs

Question 20

how to predict the shape of a molecule

Answer 20

1. find the central atom
2. work out the number of electrons in outer shell
3. work out how they are bonded and shared
4. find the number of electron pairs
5. compare electron pairs to bonds
6. compare electron pairs, lone pairs, bonding pairs and centres to predict the shape

Question 21

properties of giant covalent structures

Answer 21

• high melting points
• hard
• good thermal conductors
• insoluble
• cant conduct electricity

Question 22

what is graphite

Answer 22

carbon atoms form sheets. each carbon connected to 3 leaving outer electron to move freely and conduct electricity

Question 23

what is graphene

Answer 23

a single layer of graphite. joined in hexagons. 1 atom thick, can conduct, strong, transparent, light

Question 24

properties of giant metallic latices

Answer 24

• high melting point
  -malleable
  -ductile
  -good thermal conductor
• insoluble
• good electrical conductor

Question 25

what is electronegativity

Answer 25

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

Question 26

why does electronegativity increase across periods and up groups

Answer 26

the elements have higher nuclear charge and smaller atomic radii

Question 27

what is polarisation

Answer 27

when the two bonding atoms have different electronegativities so the bonding electrons are pulled to the more electronegative atom creating a charge

Question 28

what is a dipole

Answer 28

a difference in charge between two atoms caused by a shift in electron density in the bond

Question 29

using the pauling scale to work out ionic character

Answer 29

the higher the difference in electronegativity the higher the ionic character
1. work out the difference in ionic character
2. compare to ionic character scale

Question 30

what makes a polar molecule

Answer 30

an overall dipole caused by the presence of a permanent charge

Question 31

what are the three types of intermolecular forces

Answer 31

london forces
permanent dipole
hydrogen bonding

Question 32

what do london forces do

Answer 32

cause all atoms and molecules to be attracted to each other

Question 33

how do london forces work

Answer 33

1. electrons move quickly and are likely to be on one side that the other so a temporary dipole is created
2. this induces another opposite dipole on the neighboring atom. the two dipoles then attract and the process repeats
3. as electrons constantly move and dipoles are created and destroyed the overall affect is that the atoms are attracted

Question 34

what structure do london forces make

Answer 34

simple molecular structures

Question 35

more electrons and bigger electron cloud =

Answer 35

more london forces so stronger molecule therefore higher melting and boiling points

Question 36

what is a permanent dipole - permanent dipole bond

Answer 36

delta + and delta - charges on polar molecules cause weak electrostatic forces of attraction between molecules.
these occur alongside london forces so generally have higher melting and boiling points than molecules that cant form these

Question 37

what is a hydrogen bond