electrons + bonding + structure

Question 1

why do different molecules have different shapes and specific angles

Answer 1

because bonds repel each other equally, as they contain electrons which are negative, and so are repulsed as far as possible from other electrons

Question 2

electronegativity definition

Answer 2

the ability for the nucleus of an atom to attract a shared pair of electrons towards itself in a covalent bond

Question 3

dipole definition

Answer 3

small regions of opposite charges in a molecule due to electronegativity differences

Question 4

why do lone pairs change the angles

Answer 4

electrons in lone pairs repel more than bond pairs, and this pushes the bond pairs closer together, changing the bond angles

Question 5

3 most electronegative elements

Answer 5

nitrogen
oxygen
fluorine (most)

Question 6

polar bonds definition

Answer 6

covalent bonds between atoms with an electronegativity difference
- the bigger the difference the more polar the bond will be
- occurs in asymmetrical molecules

Question 7

3 types of intermolecular forces

Answer 7

induced dipole-dipole (london forces)
permanent dipole-dipole
hydrogen bonds (strongest)

Question 8

what are london forces

Answer 8

intermolecular forces that exist between atoms and molecules with electrons
formed because electrons within a molecule can move from one end to another, creating an instantaneous dipole
this induced a dipole in neighbouring atoms, opposite attraction induces force

Question 9

what are permanent dipole-dipole forces

Answer 9

these exist in molecules with a permanent polarity
opposite attraction induces intermolecular force
since the dipole is permanent, these are stronger than london forces
if a molecule has permanent dipole-dipole forces it also has london forces

Question 10

what are hydrogen bonds

Answer 10

occurs when a hydrogen on a molecule forms a bond with a lone pair on one of the 3 most electronegative elements (NOF)
the strongest of the 3 intermolecular forces
if a molecule has hydrogen bonds it also has permanent dipole-dipole and london forces

Question 11

simple covalent bonds
- state at room temp
- electrical conduction
- water soluble
- melting/boiling point

Answer 11

state - liquid or gas
electrical conduction - no as no mobile charge carriers
water soluble - yes if polar
melting/boiling point - low as only breaking weak intermolecular forces

Question 12

giant ionic lattice
- state at room temp
- electrical conduction
- water soluble
- melting/boiling point

Answer 12

state - gas
electrical conductivity - yes if molten as ions are able to move around + act as mobile charge carriers
water soluble - yes as polar
melting/boiling point - high as many strong ionic bonds need to be broken

Question 13

giant covalent structure
- state at room temp
- electrical conduction
- water soluble
- melting/boiling point

Answer 13

state - solid
electrical conductivity - no except graphite
water soluble - no
melting/boiling point - high as strong covalent bonds need to be broken, difficult to melt so sometimes sublime instead

Question 14

metallic bonding
- state at room temp
- electrical conduction
- water soluble
- melting/boiling point

Answer 14

state - solid
electrical conductivity - yes as has delocalised electrons which act as mobile charge carriers
water soluble - no
melting/boiling point - high as many strong metallic bonds need to be broken

Question 15

how do the 4s and 3d electron shells normally fill up

Answer 15

4s shell is at a slightly lower energy level than 3d so it fills up first
first in first out scenario - 4s electrons are the first to fill and the first to empty

Question 16

what are the 2 exceptions

Answer 16

Cu copper
and
Cr chromium

Question 17

what is different about the electron configurations of Cu and Cr

Answer 17

Cr:
the electron configuration of Cr is [Ar] 4s1 3d5 instead of [Ar] 4s2 3d4
this is because a half filled energy level (3d5) is more stable than a partially filled one (3d4)
Cu:
the electron configuration of Cu is [Ar] 4s1 3d10
instead of [Ar] 4s2 3d9
this is because a fully filled energy level is more stable than a partially filled one

hence in both cases, one electron is moved from 4s to 3d
stability gained outweighs energy needed to move electron

Question 18

covalent bond definition

Answer 18

the sharing of electrons between 2 atoms in order to obtain a full outer shell

Question 19

dative bond

Answer 19

a covalent bond where 1 atom donates both electrons to form a bond

Question 20

what is the shape of an s orbital

Answer 20

round + circular/spherical

Question 21

what is the shape of a p orbital

Answer 21

figure 8 shaped

Question 22

how many p orbitals are there

Answer 22

3 - px py and pz
each holds 2 electrons so p subshell holds 6 total

Question 23

how many electrons can a single orbital hold

Answer 23

2

Question 24

electron orbital definition

Answer 24

a region within an atom that can contain up to 2 electrons that orbit around the nucleus of an atom

Question 25

how is the structure of graphene related to the structure of graphite

Answer 25

• both form hexagonal planes
• in both the C atoms only form 3 bonds with 1 electron pair becoming delocalised
• graphene is a single layer, graphite consists of multiple that are able to slide over each other