Electrons, bonding and structure

Question 1

how many orbitals and electrons does each sub-shell have

Answer 1

s) 1 orbital, 2 electrons
p) 3 orbitals, 6 electrons
d) 5 orbitals, 10 electrons
f) 7 orbitals, 14 electrons

Question 2

what is the difference in the shape of s and p orbitals

Answer 2

s orbitals are circular, p orbitals are dumbbell-shaped

Question 3

define an atomic orbital

Answer 3

a region around the nucleus that can hold up to 2 electrons with opposite spins

Question 4

explain how electron configuration works

Answer 4

• electrons fill lowest energy orbitals first
• fill those of equal energy before pairing up and opposing spins
• Aufbaus principles

Question 5

what is covalent and dative covalent bonding

Answer 5

• electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
• the larger the bond enthalpy, the stronger the covalent bond
• in dative covalent bonding, both electrons come from one bonding atom

Question 6

describe diamond as a giant covalent lattice

Answer 6

• each C is bonded to 4 other C atoms
• tetrahedral arrangement
• cannot conduct electricity
• extremely hard
• insoluble
• very high melting point
• good thermal conductor
• good electrical insulator

Question 7

describe graphite as a giant covalent lattice

Answer 7

• each C is bonded to 3 other C atoms
• hexagonal pattern
• a delocalised electron
• soft and slippery
• less dense than diamond
• high melting and boiling point
• weak intermolecular forces between layers
• can conduct electricity

Question 8

describe graphene

Answer 8

• single sheet of graphite
• each C bonded to 3 others and has a delocalised electron
• electrical and thermal conductivity
• strong
• transparent and lightweight

Question 9

describe silicon

Answer 9

• tetrahedral shape
• each silicon atom is bonded to 4 other silicon atoms
• strong covalent bonds
• very high melting and boiling point
• hard and brittle
• doesn’t conduct electricity

Question 10

what is ionic bonding, specifically in an ionic lattice

Answer 10

• electrostatic force of attraction between to oppositely charged ions ( metal and non metal )
• ionic lattices have high melting and boiling points, can conduct electricity when molten/in solution not solid, and dissolve in water

Question 11

explain metallic bonding

Answer 11

• electrostatic attractions between positively charged cations and negatively charged delocalised electrons
• strength depends on number of delocalised electrons per atom, charge of metal cation and radius of metal cation but they’re usually strong
• malleable and ductile, insoluble, good conductors of electricity and heat and have high melting and boiling points

Question 12

explain linear, non-linear, trigonal planar and tetrahedral bond shapes

Answer 12

linear) 2 bonding and 0 lone electrons, bond angle 180
non-linear) 2 bonding and 0 lone electrons, bond angle 104.5
trigonal planar) 3 bonding and 0 lone electrons, bond angle 10]
tetrahedral) 4 bonding and 0 lone electrons, bond angle 109.5

Question 13

explain trigonal pyramidal, trigonal bi-pyramidal and octahedral bond shapes

Answer 13

trigonal pyramidal) 3 bonding and 1 lone electrons, bond angle 107
trigonal bi-pyramidal) 5 bonding and 0 lone electrons, bond angle 120 and 90
octahedral) 6 bonding and 0 lone electrons, bond angle 90 and 90

Question 14

show repulsion of lone and bonding pairs of electrons from largest to smallest repulsion

Answer 14

lone pair - lone pair
lone pair - bonding pair
bonding pair - bonding pair

Question 15

define electronegativity

Answer 15

• the ability to attract bonding electrons
• measured on the Pauling scale, higher score means higher electronegativity

Question 16

what are the 3 factors affecting electronegativity

Answer 16

• atomic radius
• shielding
• nuclear charge

Question 17

describe the trends in electronegativity on the periodic table

Answer 17

• increases across a period
• decreases down a group

Question 18

explain polar bonds in terms of electronegativity

Answer 18

• bonding electrons are slightly more attracted to the more electronegative element
• creates a dipole which doesn’t cancel out due to asymmetric arrangement

Question 19

how can electronegativity be used to predict bond type

Answer 19

< 1.0 = non polar covalent
1.0 to 2.0 polar covalent
> 2.0 ionic

Question 20

explain induced dipole dipole forces ( london / van der waal forces )

Answer 20

• present in all atoms/molecules
• occur due to fluctuations in electron distribution around an atom where a temporary dipole is formed which can further induce other dipoles
• strength affected by size and surface area

Question 21

explain permanent dipole dipole forces

Answer 21

• present in polar molecules due to unequal sharing of electrons
• creates a partial positive and negative charge with electrostatic attraction between them

Question 22

explain hydrogen bonding

Answer 22

• strongest intermolecular force
• type of permanent dipole-dipole force where hydrogen bonds to a highly electronegative element ( F,N,O ) that has a lone pair of electrons
• highly polar

Question 23

how does the type of intermolecular force influence the physical properties of simple molecular substances

Answer 23

• melting and boiling points
• solubility in water
• electrical conductivity