2.2 electrons, bonding and structure

Question 1

define an orbital

Answer 1

spaces in an atom where electrons are found in an opposite spin pair

Question 2

what is the shape of an s orbital?

Answer 2

spherical

Question 3

what is the shape of a p orbital?

Answer 3

dumbbell shape

Question 4

how many electrons can the s subshell hold?

Answer 4

2 electrons of opposite spins (one box/orbital)

Question 5

how many electrons can the p subshell hold?

Answer 5

6 electrons paired up with opposite spins (3 boxes/orbitals)

Question 6

how many electrons can the d subshell hold?

Answer 6

10 electrons paired up with opposite spins (5 boxes/orbitals)

Question 7

how many electrons can the f subshell hold?

Answer 7

14 electrons paired up with opposite spins (7 boxes/orbitals)

Question 8

name the 3 rules of orbitals

Answer 8

1. electrons fill up from the lowest available energy level
2. two electrons of opposite spins in each orbital (box)
3. when an energy level is not full, the electrons occupying it will try to remain unpaired

Question 9

name 2 transition metals that do not follow the box notation pattern and explain why this occurs

Answer 9

chromium - has a 4s1 then 3d5 - instead of having 4s2 then 3d4, electron from the 4s orbital moves to the 3d one so they are both partially full which is more stable.

copper - has 4s1 and 3d10 - having a partially full 4s orbital and a full 3d orbital is more stable than having a fun 4s one and an almost full 3d one.

Question 10

which energy level fills up first, 4s or 3d?

Answer 10

4s - because 4s is lower in energy than 3d so it fills up first.

Question 11

what is the rule for forming transition metal ions?

Answer 11

ONLY for transition metals - when forming ions, the electrons in the 4s orbital are removed FIRST.

Question 12

define the term ionic bond

Answer 12

the electrostatic force of attraction between oppositely charged ions

Question 13

what kind of structures to ionic compounds form?

Answer 13

giant ionic lattice structures

Question 14

name and describe 4 properties of ionic compounds

Answer 14

1. high melting/boiling point - strong electrostatic forces require a lot of energy to be broken
2. weak strength/brittle - moving layers of ions brings the same charged ions into close contact causing repulsion, and the forces being weakened, causing the lattice to break.
3. only conduct electricity in a liquid/aqueous form - when molten or dissolved, ions can move and carry charge.
4. soluble in water - water is polar, and so it attracts the ions away from each other, causing the lattice to break away.

Question 15

define covalent bonding

Answer 15

bonds formed between non-metals in which they share pairs of electrons in order to achieve a full outer shell.

the bond is created by a strong electrostatic attraction between the shared pair of valence electrons and the positive nuclei.

Question 16

name and describe 3 properties of simple covalent molecules

Answer 16

1. low melting/boiling point - weak intermolecular forces require little energy to be broken
2. do not conduct electricity - no mobile electrons to carry charge
3. strong covalent bonds - shared pair of electrons and strong electrostatic force hold atoms together

Question 17

what kind of structure to giant covalent compounds form?

Answer 17

lattice structures

Question 18

name 4 giant covalent compounds

Answer 18

diamond
graphite
silicon dioxide
graphene

Question 19

what is dative covalent (coordinate) bonding?

Answer 19

when one element provides a full pair of electrons so one shared pair comes from one atom.

e.g. ammonium ion (NH4+)

Question 20

name 5 properties of diamond

Answer 20

1. high melting and boiling point - strong covalent bonds
2. very hard - strong covalent bonds and lattice structure create a dense overall structure
3. thermal conductor - vibrations travel through easily because of denseness and strong bonds
4. doesn’t conduct electricity - no mobile electrons - fixed into the lattice bonding
5. won’t dissolve in any solvent

Question 21

name 5 properties of graphite

Answer 21

1. lubricant material - layers slide over each other easily due to weak intermolecular forces.
2. conducts electrons - delocalised 4th electron per carbon can move and carry charge
3. not dense - layers far apart (good for light weight but strong sports equipment)
4. high melting/boiling points - strong covalent bonds
5. insoluble in any solvent - strong covalent bonds won’t break down

Question 22

what is average bond enthalpy?

Answer 22

the average amount of energy required to break a particular bond

Question 23

what is the order of repulsion between lone and bonded pairs of electrons? (most - least)

Answer 23

2 lone pairs have the most repulsion
then lone and bonded pairs
then 2 bonded pairs have the least repulsion

Question 24

what shape would a molecule with 2 bonded electron pairs have? what angle would they have?

Answer 24

linear molecules

180 degrees

Question 25

what shape would a molecule with 3 bonded electron pairs have? what angle would they have?

Answer 25

trigonal planar | 120 degrees

Question 26

what shape would a molecule with 4 bonded electron pairs have? what angle would they have?

Answer 26

tetrahedral | 109.5 degrees

Question 27

what shape would a molecule with 3 bonded electron pairs and one lone pair have? what angle would they have?

Answer 27

(trigonal) pyramidal | 107 degrees

Question 28

what shape would a molecule with 2 bonded electron pairs and 2 lone pairs have? what angle would they have?

Answer 28

non-linear/bent | 104.5 degrees

Question 29

what shape would a molecule with 5 bonded electron pairs have? what angle would they have?

Answer 29

trigonal bipyramidal | 120 and 90 degrees

Question 30

what shape would a molecule with 6 bonded electron pairs have? what angle would they have?

Answer 30

octahedral | 90 degrees

Question 31

define electronegativity

Answer 31

the ability of an atom to attract the bonding electron pairs in a covalent bond

Question 32

na6me 2 trends of electronegativity in the periodic table

Answer 32

increases from left to right (towards halogens) | increases from bottom to top (towards smaller atoms)

Question 33

define polar bond

Answer 33

a bond in which the electrons are unevenly distributed (or there is a permanent dipole) due to a difference in electronegativity

Question 34

define polar molecule

Answer 34

a molecule where there is a net/overall dipole moment, causing a partially negative area (ẟ⁻) and a partially positive area (ẟ⁺) / polar molecules arranged asymmetrically

Question 35

define a dipole

Answer 35

a difference in polarity

Question 36

define inTERmolecular force

Answer 36

an attraction between molecules

Question 37

define inTRAmolecular force

Answer 37

an attraction between atoms, holding them together usually

Question 38

name the three intermolecular forces. whats their order of strength?

Answer 38

induced dipole-dipole - weakest permanent dipole-dipole - middle strongest hydrogen bonds - strongest

Question 39

whats an induced dipole-dipole intermolecular force?

Answer 39

instantaneous intermolecular bond between moving electrons.

Question 40

what happens to strength of intermolecular forces and melting and boiling points as atom size increases? why?

Answer 40

as atom size increases, the intermolecular force strength increases. this is because as atom size increases, electron number increases meaning more electron will cause a larger partial charge and therefore a stronger induced dipole-dipole interactions. stronger interactions require more energy to be broken = higher melting + boiling point.

Question 41

whats a permanent dipole-dipole intermolecular force?

Answer 41

constant force between polar molecules

Question 42

what is a hydrogen bond?

Answer 42

an intermolecular force occurring between hydrogen atom and another atom with a large difference in electronegativity. the hydrogen bonds to a lone pair of electrons.

Question 43

which atoms does hydrogen bond to in a hydrogen bond? why?

Answer 43

oxygen, nitrogen and fluorine. | because the dipole is so strong because of the difference in electronegativity.

Question 44

name 5 unusual properties of water

Answer 44

``` higher mp and bp than usual ice is less dense than water high surface tension higher viscosity cohesion ```

Question 45

why does water have a higher mp and bp ?

Answer 45

hydrogen bonds are stronger than other intermolecular bonds because they can stretch over a long distance so need more energy to be overcome.

Question 46

why is ice less dense than liquid water?

Answer 46

the structure of ice is a regular lattice. the long hydrogen bonds hold the molecules far apart creating a larger volume with the same mass of water.

Question 47

what is viscosity?

Answer 47

how thick a liquid is

Question 48

why does water have a higher viscosity than other like structures?

Answer 48

the strong hydrogen bonds create a resistance to flow

Question 49

why does water have high surface tension?

Answer 49

the water molecules at the surface of the water are bonded to the molecules below them. these hydrogen bonds below hold up the surface molecules.

Question 50

what is cohesion?

Answer 50

attraction between molecules of the same substance

Question 51

why does water have cohesion?

Answer 51

each water molecule could have up to 4 hydrogen bonds, causing greater attraction and greater cohesion.