3.1 The periodic table

Question 1

How are elements in the periodic table arranged?

Answer 1

• by increasing atomic
  (proton) number
• in periods showing repeating trends in physical and chemical properties
• in groups having similar chemical properies

Question 2

What is the periodic trend in electron configuration across periods 2 and 3?

Answer 2

Across period 2 - 2 electrons fill the 2s sub-shell before 6 electrons fill the 2p sub-shell Across period 3 - 2 electrons fill the 3s sub-shell before 6 electrons fill the 3p sub-shell

Question 3

Definition of ‘first ionisation energy’

Answer 3

the energy required to remove 1 electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 4

What are the factors affecting ionisation energy

Answer 4

atomic radius
nuclear charge
electron shielding
nuclear attraction

Question 5

What are the trends of first ionisation trends across a period

Answer 5

atomic radius slightly decreases
electron shielding stays the same
nuclear charge increases as there are more protons nuclear attraction increases across so a higher ionisation energy needed

Question 6

What are the trends of first ionisation trends down a group?

Answer 6

atomic radius increases - more shells
electron shielding increases - more shells
nuclear charge decreases
weak nuclear attraction so less energy required to remove an electron
ionisation energy decreases down a group

Question 7

Describe the variation of melting points across periods 2 and 3?

Answer 7

groups 1 - 14 melting points increase steadily, giant metallic (higher nuclear charge, strong attraction) and covalent structure

group 14 - 15 sharp decrease in melting points, simple molecular structures - weak intermolecular structures

group 15 - 18 melting points stay relatively low, simple molecular structures

Question 8

Describe variance in first ionisation energy between groups 2 and 3(13)?

Answer 8

overall ionisation energy increases across a period between groups 2 and 13 (Be to B, Mg to Al) - slight decrease
group 13 - p orbital
group 2 - s orbital
p orbital have higher energy than s orbitals so they are marginally further away from the nucleus
meaning that electrons p orbitals are slightly easier to remove so elements have lower ionisation energies

Question 9

Why is there decrease in first ionisation energy between groups 15 and 16?

Answer 9

similar decrease to group 2 and 13
15 and 16 - (N to O, P to S)
group 13 - 18 all electrons in p orbital
groups 13, 14, 15 - each p orbital contains a single electron
group 16 - outermost electron is spin paired so there is some repulsion - making electron easier to remove so less ionisation energy needed

Question 10

What is metallic bonding?

Answer 10

strong electrostatic attraction between cations(+) and delocalised electrons

Question 11

What are metallic bonding properties?

Answer 11

high melting/boiling points
ductile
malleable

Question 12

Define ‘giant metallic lattice’

Answer 12

a 3d structure of positive ions and delocalised electrons, bounded by strong metallic bonds

Question 13

Define ‘giant covalent lattice’

Answer 13

a 3d structure of atoms that are all bonded together by strong covalent bonds

Question 14

What are the structure and properties of diamond?

Answer 14

4 strong covalent bonds per atom
tetrahedral shape - 109.4
high melting point
hard
non- conducting

Question 15

What are the structure and properties of graphene?

Answer 15

2d giant lattice
1 carbon atom thick of interlocking hexagonal carbon rings
extremely strong
very light
conducts electricity

Question 16

What are the structure and properties of graphite?

Answer 16

3 strong covalent bonds + 1 delocalised electron
trigonal planar (planes of atoms in hexagons) - 120 high melting point
soft - layers slide
conducts electricity - delocalised electrons

Question 17

What are the physical properties of giant covalent lattices?

Answer 17

high melting and boiling point
non-conductors of electricity - no free charged particles (except graphite)
insoluble in polar and non-polar solvents - covalent bonds too strong

Question 18

What are the physical properties of giant metallic lattices?

Answer 18

high melting and boiling point - strong attraction between positive ions and negative delocalised electrons
good electrical conductivity - delocalised electrons can move freely, even in solid state
malleable and ductile - delocalised electrons can move so the atoms or layers can slide past each other

Question 19

What are the trends in melting point across period 2 and 3?

Answer 19

melting point increases from Group 1 to Group 14 - elements have giant structures (metallic then covalent)
melting points decrease from Group 14 to Group 15 because the structure changes to simple molecular - only held together by weak intermolecular forces

Question 20

Group 2 metals + oxygen

Answer 20

metal oxide
vigorous reaction

Question 21

Group 2 metals + water

Answer 21

metal hydroxide + hydrogen gas
beryllium doesnt react
mg reacts very slowly - vigour increasing as you go down
redox

Question 22

Group 2 metals + dilute acid

Answer 22

salt + hydrogen gas
beryllium doesnt react
reaction more vigorous going down

Question 23

Where are the s-, p-, d- and f- blocks on the periodic table?

Answer 23

s d p
f

Question 24

What are the trends in reactivity down group 2 in terms of 1st and 2nd ionisation energies?

Answer 24

2 outer electrons lost more easily going down the group reactivity increases going down the group ionisation energy decreases

Question 25

What is the trend in the increasing alkalinity of group 2 metals?

Answer 25

alkalinity increases down group 2 when reacting with water they form more soluble metal hydroxides - releases more OH- ions, making it more alkaline with higher pH

Question 26

How do group 2 metals neutralise acidic soils?

Answer 26

calcium hydroxide ('lime') - Ca(OH) 2 -reduces acidity level of soil

Question 27

How do group 2 metals help indigestion?

Answer 27

in the stomach too much hcl - indigestion magnesium hydroxide - Mg(OH)2 and calcium carbonate - CaCO3 - acts as an antacid -neutralises the excess acid and produces salt and water acid + metal --- salt + water

Question 28

What type of molecules are halogens?

Answer 28

diatomic

Question 29

Describe the trend in boiling point in halogens?

Answer 29

down the group boiling point increases and physical state changes from gas - liquid - solid because each element has extra shell of electrons - leading to higher level of London forces (induced dipole - dipole) between molecules more energy needed to remove an electron so increased boiling point reactivity decreases

Question 30

Describe the electron configuration of halogens/group 7/group 17 ?

Answer 30

7 outer shell electrons xs2 xp5 gain 1 electron to form 1- ions - halide ions

Question 31

Describe the reactivity of halogens?

Answer 31

very reactive and highly electronegative - good at attracting electrons reactivity and oxidising power decrease down the group atomic radius decreases electron shielding increases ability to gain electron from p-subshell to form 1- ion decreases

Question 32

What colour do the 3 halogens change in water?

Answer 32

Cl - pale green Br - orange I - brown

Question 33

What colour do the 3 halogens change in cyclohexane?

Answer 33

Cl - pale green Br - orange I - violet

Question 34

Define 'disproportionation'

Answer 34

oxidation and reduction of the same element

Question 35

What is the full equation of a reaction of chlorine with water (disproportionation)?

Answer 35

Cl2(aq) + H2O(aq) ---> HClO(aq) + HCl(aq) Chlorine is oxidised in HClO from 0 to +1 Chlorine is reduced in HCl from 0 to -1

Question 36

What is the full equation of a reaction of chlorine with cold, dilute, aqueous NaOH (disproportionation)?

Answer 36

Cl2(aq) + 2NaOH(aq) ---> NaCl(aq) + NaClO(aq) + H2O(l) Chlorine is oxidised in NaClO from 0 to +1 Chlorine is reduced in NaCl from 0 to -1 NaClO = bleach

Question 37

What are the benefits of chlorine in water treatment?

Answer 37

kills bacteria eradicated water-carried diseases e.g. cholera and dysentery

Question 38

What are the risks and ethical considerations of using chlorine in water treatment?

Answer 38

chlorine is a toxic gas chlorine can form chlorinated hydrocarbons, causing cancer peru stopped water treatment - cholera outbreak people cant choose if they want chlorine in their water or not - unfair

Question 39

What is the ionic equation of chlorine oxidising bromine and the colour change in water and cyclohexane?

Answer 39

Cl2(aq) + 2Br-(aq) --> 2Cl-(aq) + Br2(aq) water: orange cyclohexane: orange

Question 40

What is the ionic equation of chlorine oxidising iodine and the colour change in water and cyclohexane?

Answer 40

Cl2(aq) + 2I-(aq) --> 2Cl-(aq) + I2(aq) water: brown cyclohexane: violet

Question 41

What is the ionic equation of bromine oxidising iodine and the colour change in water and cyclohexane?

Answer 41

Br2(aq) + 2I-(aq) --> 2Br-(aq) + I2(aq) water: brown cyclohexane: violet

Question 42

What is the ionic equation for Cl- with AgNO3 and NH3?

Answer 42

Ag+ (aq) + Cl- (aq) ---> AgCl(s)

Question 43

What is the ionic equation for Br- with AgNO3 and NH3?

Answer 43

Ag+ (aq) + Br- (aq) ---> AgBr(s)

Question 44

What is the ionic equation for I- with AgNO3 and NH3?

Answer 44

Ag+ (aq) + l- (aq) ---> Agl(s)

Question 45

Describe the test for halide ions

Answer 45

1. dissolve halide in water 2. add silver nitrate (aq) 3. colour change - Cl(white), Br(cream), I(yellow) 4. if colour hard to tell - add dilute ammonia 5. Cl(soluble in dilute), Br(soluble in concentrated), I(insoluble)

Question 46

Describe the test for carbonate ions and give the equation

Answer 46

CO3 2-(aq) + 2H+(aq) --> H20(aq) + CO2(g) 1. add dilute strong acid to solution 2. pass any gas formed through limewater 3. gas should turn limewater cloudy

Question 47

Describe the test for sulfate ions and give the equation

Answer 47

Ba 2+(aq) + SO4 2-(aq) --> BaSO4(aq) 1. add dilute HCl and barium chloride barium sulfate produces a white precipitate

Question 48

Describe the test for ammonium ions and give the equation

Answer 48

NH4 +(aq) + OH-(aq) --> NH3 (aq) + H2O (aq) 1. add NaOH to solution and gently warm 2. test any gas with red litmus paper ammonia gas - red litmus paper - blue - has distinctive smell (hazardous)