Physical 1: Bonding

Question 1

what is ionic bonding?

Answer 1

strong electrostatic forces of attraction between oppositely charged ions held in a lattice

Question 2

give an example of an ionically bonded substance

Answer 2

NaCl

Question 3

how high are ionically bonded substances’ boiling point and melting point?

Answer 3

high - takes lots of energy to break strong electrostatic forces of attraction between oppositely charged ions

Question 4

do ionic compounds conduct electricity?

Answer 4

yes, when molten/in solution as the ions are free to move and carry charge
they don’t when solid

Question 5

what is simple molecular covalent bonding?

Answer 5

strong covalent bonds between atoms, weak van der waals forces of attraction between molecules

Question 6

are there any lone electrons in simple covalent bonding?

Answer 6

no - all involved in bonding

Question 7

can simple molecular covalent molecules conduct electricity?

Answer 7

no - all electrons used in bonding and aren’t free to move

Question 8

do simple molecular substances have a high/low mpt and bpt?

Answer 8

low - weak vdw forces of attraction between molecules that don’t take much energy to overcome (these are overcome rather than covalent bonds)

Question 9

describe macromolecular covalent bonding

Answer 9

lattice of many atoms held together by strong covalent bonds

Question 10

do substances with macromolecular covalent bonds have high/low mpt and bpts?

Answer 10

high, as it takes a lot of energy to overcome many strong covalent bonds

Question 11

do substances with macromolecular covalent bonds conduct electricity?

Answer 11

most don’t as all electrons are used in bonding

Question 12

describe the structure of diamond

Answer 12

3D tetrahedral structure of C atoms, with each C atom bonded to four others

Question 13

describe the structure of graphite

Answer 13

• macromolecular covalent
• each C atom is bonded to 3 others, so it is in layers
• weak vdws between layers mean they can slide over each other —- soft and slippery
• one electron from each carbon is delocalised and can carry charge —- conducts electricity

Question 14

describe metallic bonding

Answer 14

• lattice of positive metal ions strongly attracted to a sea of delocalised electrons
• layers can slide over each other —- malleable

Question 15

do metallic compounds have high/low bpt and mpt?

Answer 15

high as strong forces of attraction between positive metal ions and negatively charged sea of delocalised electrons

Question 16

do metallic compounds conduct electricity?

Answer 16

yes, as the delocalised electrons can move throughout the metal in carry charge

Question 17

how does the strength of metallic bonds change across the periodic table?

Answer 17

• increases — higher mp and bp
• higher charge on metal ions
• more delocalised electrons per ion
• stronger force of attraction between them

Question 18

define electronegativity

Answer 18

the ability of an atom to attract the pair of electrons (the electron density) in a covalent bond

Question 19

what affects electronegativity?

Answer 19

• nuclear charge
• atomic charge
• electron shielding

Question 20

what is the most electronegative element?

Answer 20

Fluorine (4.0 on Pauling’s scale) – has the largest nuclear charge for its electron shielding – small atomic radius

Question 21

how do you get a nonpolar bond?

Answer 21

both bonding elements have the same electronegativities

Question 22

when do you get a polar bond?

Answer 22

bonding atoms have a different electronegativities

Question 23

what is the strongest type of intermolecular force ?

Answer 23

hydrogen bonding

Question 24

what is the weakest type of intermolecular force?

Answer 24

van der waals forces

Question 25

describe van der waal's forces of attraction

Answer 25

- temporary dipoles are created by the random movement of electrons - induces dipole in neighbouring molecule - temporary induced dipole-dipole attraction aka vdw forces

Question 26

are van der waals forces stronger in smaller or larger molecules?

Answer 26

larger - more electrons

Question 27

describe permanent dipole-dipole attractions

Answer 27

some molecules with polar bonds have permanent dipoles --- forces of attraction between those dipoles and those of neighbouring molecules

Question 28

what conditions are needed for hydrogen bonding to occur?

Answer 28

- O-H, N-H or F-H bond, lone pair of electrons of O, F, N - because O, N, and F are highly electronegative, H nucleus is left exposed - strong force of attraction between H nucleus and lone pair of electrons on O, N, F

Question 29

why is ice less dense than liquid water?

Answer 29

- in liquid water, hydrogen bonds constantly break and reform as molecules move about - in ice, hydrogen bonds hold the molecules in fixed positions; this makes them slightly further apart than in liquid water

Question 30

what is a dative/co-ordinate covalent bond?

Answer 30

formed when an electron deficient atom/ion with a lone pair of electrons (not used in bonding)

Question 31

what does the shape of molecules depend on?

Answer 31

- number of electrons in the valence shell of the central atom - number of these electrons which are in bonded or lone pairs

Question 32

what does the electron pair repulsion theory state?

Answer 32

the electron pairs will take up positions as far away from each other as possible, to minimise the repulsive forces between them

Question 33

which experience the most repulsion of lone/bonding pair repulsion?

Answer 33

lone pair-lone pair is the strongest repulsion lone pair-bonding pair is the middle repulsion bonding pair-bonding pair is the weakest repulsion

Question 34

what is the shape, diagram and bond angle in a shape with 2 bonded pairs and 0 lone pairs?

Answer 34

linear 180 degrees o----o----o

Question 35

what is the shape, diagram and bond angle in a shape with 3 bonded pairs and 0 lone pairs?

Answer 35

trigonal planar | 120 degrees

Question 36

what is the shape, diagram and bond angle in a shape with 4 bonded pairs and 0 lone pairs?

Answer 36

tetrahedral | 109.5 degrees

Question 37

what is the shape, diagram and bond angle in a shape with 5 bonded pairs and 0 lone pairs?

Answer 37

trigonal bipyramid | 90 degrees and 120 degrees

Question 38

what is the shape, diagram and bond angle in a shape with 6 bonded pairs and 0 lone pairs?

Answer 38

octahedral | 90 degrees