inorganic chemistry

Question 1

what are the different areas of the table in terms of electronic arrangement

Answer 1

s, block, p-block, d - block and the f block

Question 2

how do we know if an element is in the s-block

Answer 2

an element is in the s block if its highest energy electron is in the s-orbital

e.g. Na 1s2 2s2 2p6 3s1

Question 3

how do we know if an element is in the p- block

Answer 3

an element is in the p block if its highest energy electron is in the p - orbital

e.g. C
1s2 2s2 2p2

Question 4

how do we know if an element is in the d -block

Answer 4

an element is in the d - block if the highest energy electron is in the d - orbital

e.g. Fe
1s2 2s2 2p6 (…) 3d6

Question 5

what are the differences between the transition metals and the d - blocks

Answer 5

the transition metals and d - block elements are not exactly the same

e.g. scandium and zinc are, not transition metals because they do not form any compounds in which they have partly filled d- orbitals, which is the characteristics of transition metals

Question 6

what are the origins of the terns s,p,d, and f

Answer 6

• when elements are heated they give out light at certain wavelengths as excited electrons fall back from one energy level to a lower

This causes lines to appear in the spectrum of light they give out
The letters s, p, d and f stands for words that were used to describe the lines

S- FOR SHARP
P - FOR PRINCIPLE
D - FOR DIFFUSE
F - FOR FINE

Question 7

what is the s-group

Answer 7

a group is a vertical column of elements
The elements in the same group form a chemical “family” - they have similar properties

elements in the same group have the same number of electrons in the outer main level

Question 8

what is the reactivity of the elements in s - block

Answer 8

in the s-block, elements (metals) get more reactive going down a group

Question 9

what is the general reactivity of the non -metals

Answer 9

non - metals elements tend to get more reactive going up a group

Question 10

what is the general reactivity of the transition elements

Answer 10

transition elements are a block of rather unreactive metals

this is where the most useful metals are found

Question 11

what are periods

Answer 11

are horizontal rows of elements the periods are numbered stating from Period 1 which contains only hydrogen and helium

period 2 contains the elements lithium to neon and so on

There are trends as you go across a period

Question 12

what does the term periodicity/ periodic means

Answer 12

• recurring regularly

Question 13

what can periodicity be explained by ( the recurring trend in the periodic table)

Answer 13

the electron arrangement of the elements

e.g. the elements in group 1, 2 and 3 (sodium, magnesium and aluminium) are metals
They have GIANT STRUCTURES
they lose their outer electrons to form ionic compounds

Silicon in group 4 has four electrons in its outer shell with it forms four covalent bonds
The elements have METALLIC properties and are classed as a SEMI - METALS

the elements in group 5,6 and 7 are NON - METALS
either accept electrons to form ionic compounds or share their electrons to form COVALENT COMPOUNDS

Argon in Group 0 is a NOBLE GAS - it has a full outer shell and is UNREACTIVE

Question 14

what is the “clear cut” in terms of the trend in the melting and boiling points

Answer 14

there is a clear break in the middle of the figure between elements that have a high melting point on the left and those with low melting points on the right

Question 15

what can explain the trends of the melting and boiling points in the periodic table

Answer 15

these trends are due to their structures

• giant structures tend to have high melting and boiling points (on left)
• molecular or atomic structures (on right) tend to have low melting and boiling points

Question 16

why do the melting points of the metals increase from sodium to aluminium

Answer 16

due to the increased strength of the metallic bonding

as you go from the left to the right the charge on the ion increases so more electrons join the delocalised electron “sea” that holds the giant metallic structure together

Question 17

what does the melting points of the non -metals depend on

Answer 17

the size of the van Der Waals forces between the molecules

This, in turn, depends on the number of electrons in the molecule and how closely the molecule is packed together

as a result, the melting points of these non-metals are

S4 > P4 > CL2

Question 18

what do the atomic radii tell us

Answer 18

it tells us the size of atoms

Question 19

why can’t you measure the radius of an isolated atom

Answer 19

you can’t measure the radius of an isolated atom because there is no clear point at which the electron cloud density around it drops to 0

instead, half the distance between the centres of a pair of atoms is used

Question 20

why does the atomic radius of an element differ

Answer 20

• atomic radius is a general term

it depends on the type of bond that is forming - covalent, ionic, metallic, van der Waals

the covalent radius is most commonly used as a measure of the size of the atom

Question 21

why are noble gases often left out of comparisons of atomic radii

Answer 21

even metals can form covalent molecules such as Na2 in the gas phrase

since noble gases do not bond covalently with one another they do not have covalent radii and so they are often left out of comparisons in atomic radii

Question 22

why do the radii of atoms decrease across a period

Answer 22

• we can explain this trend by looking at the electronic structures of elements in a period
  e. g. sodium to chlorine in period 3

as you move from Na to Cl you are adding protons to the nucleus and electrons to the outer main level, the third shell ( the same shell), the charge increases from + 11 to +17

this increased charge pulls the electrons in closer to the nucleus
There are no additional electrons shells to provide more shielding so the size of the atom decreases as you go across the period

Question 23

why do the radii of atoms increase down a group

Answer 23

going down a group in the Periodic table, the atoms of each element have one extra complete main level of electrons compared with the one before

-so going down the group, the outer electron main level is further from the nucleus and the atomic radii increases

Question 24

what is the first ionisation energy

Answer 24

the first ionisation energy is the energy required to convert a mole of isolated gaseous atoms into a mole of singly positively charge gaseous ions, that is, to remove one electron from each atom

Question 25

what is the general trend for ionisation energies across a period

Answer 25

the ionisation energy increases going down any period

this is because the number of protons increases but the shielding and the number of shells stays the same

this increased nuclear charge means that it gets increasingly difficult to remove an electron

Question 26

why does the first ionisation energy decreases going down the group

Answer 26

the number of oof filled inner levels increases down the group

This results in an increase in shielding

Also, the electron to be removed is at an increasing distance from the nucleus and is therefore held less strongly

Thus the outer electrons get easier to remove going down a group because they are further away from the nucleus

Question 27

why is there a drop in ionisation energy from one period to the next

Answer 27

moving from neon in Period 0 with electron arrangement 2,8 to sodium, 2,8,1 there is a sharp drop in the first ionisation energy

This is because at sodium a new main level starts and so there is an increase in atomic radius, the outer electron is further from the nucleus, less strongly attracted and easier to remove

Question 28

a detailed look into the trends in ionisation energy in period 3

Answer 28

the first ionisation energy drops between GROUP 2 and GROUP 3 so that aluminium has lower ionisation energy than magnesium

the ionisation energy drops again slightly between GROUP 5 ( phosphorus) and GROUP 6 (sulfur)

similar patterns occur in other periods

Question 29

how do we explain the drop in the first ionisation energy across GROUP 2 and GROUP 3

Answer 29

magnesium loses an electron in 3s while magnesium loses an electron in 3p which is a higher energy level than magnesium so the electron can be lost easier

Question 30

explain the drop in the first ionisation energy between GROUP 5 and GROUP 6

Answer 30

an electron in a pair will be easier to remove than one in an orbital on its own orbital because to os being repelled by the other electron

phosphorus has no paired electrons in a p -orbital because each p -electron s in its own orbital

sulfur has two of its p – electrons paired in a p - orbital so one of these will be easier to remove than an unpaired one due to the repulsion of the other electron in the same orbital

Question 31

what are group 2 elements sometimes called

Answer 31

elements in group 2 are called the alkaline earth metals

this is because their oxides and hydroxides are alkaline

Question 32

which block is group 2 in

Answer 32

like group, they are s- block elements

they are similar to group 1 but are less reactive

Question 33

what are the physical properties of group 2

Answer 33

electron arrangement
2 electrons in outer s- orbital
This s- orbital becomes further from the nucleus going down the group

the sizes of the atoms
the atoms get bigger going down the group. The atomic (metallic) radii increases because each element has an extra filled main level of electrons compared with the one above

Question 34

explaining the trend in melting points in group 2

Answer 34

group 2 elements are metals with high melting points typical of a giant metallic structure

this is because going fon the group, the electrons in the “sea” of delocalised electrons are further away from the positive nuclei
As a result, the strength of the metallic bonds decreases going down the group
For this reason, the melting points of group 2 elements decrease slightly going down the group staring with calcium

Question 35

explain the ionisation energies in group 2

Answer 35

in all their reactions, atoms in Group 2 lose their two outer electrons to form ions with two positive charges

SO, an amount of energy equal to the sum of the first and second ionisation energies is needed for complete ionisation

Both the first ionisation energy and the second ionisation decreases going down the group - it takes less energy to remove the electrons as they become further away from the positive nucleus

The nucleus is more effectively shielded by more inner shells of electrons

Question 36

what is oxidation

Answer 36

oxidation is the loss of electrons so in all reactions the group 2 metals are oxidised

Question 37

what is the trend of group2 metals reactions with water

Answer 37

with water you see a trend in reactivity:

• metals you get more reactive going down:
  These are also redox reactions
  The basic reaction (where M is any metal in Group 2_)
  M(s) +2H2O - M(OH2)aq +H2

Question 38

why would magnesium hydroxide important

Answer 38

magnesium hydroxide is a milk of magnesia and is used in indigestion remedies to neutralise excess stomach acid

Question 39

how does magnesium react with cold water

Answer 39

magnesium reacts very slowly with cold water but rapidly with steam to form an alkaline oxide and hydrogen

Mg(s) + H2O - MgO(s) + H2

Question 40

how does calcium react with water

Answer 40

calcium react in the same way but more vigorous, even with cold water

Question 41

how do strontium and barium react with water

Answer 41

strontium and barium reacts more vigorous

Question 42

what is calcium hydroxide sometimes called

Answer 42

calcium hydroxide is sometimes slaked lime and is used to treat acidic soil

Most plants have an optimum level of acidity or alkalinity in which they thrive
e.g. grass grows best at a pH of 6

Question 43

what are the hydroxides

Answer 43

the hydroxides are all white solids

Question 44

why do all the metals in group 2 form (OH)2

Answer 44

because it is in group 2 and needs 2 hydroxides

Question 45

what are the trends in solubilities in group 2 hydroxides

Answer 45

Mg(OH)2 (magnesium hydroxide) (milk of magnesia) is almost insoluble

Ca(OH)2 calcium hydroxide, is sparingly soluble and a solution is used as lime water (slightly soluble)

Strontium hydroxide Sr(OH)2 is more soluble

Barium hydroxide Ba(OH)2 dissolves to produce alkaline solution:
Ba(OH)2(s) + aq - Ba2+(aq) + 2OH-(aq) (soluble)

Question 46

why are sulfates important

Answer 46

due to the trend in solubility in sulfates, barium sulfatesis virtually insoluble

This means that it can be taken by mouth as a barium meal to outline the gut in medical x - rays ( the heavy barium atom is very good at absorbing x - rays)

the test is safe, despite the fact that is barium compounds are highly toxic, because barium sulfate is so insoluble

Question 47

how do we test for barium sulfates

Answer 47

the insolubility of barium sulfate is used in a simple test for sulfate ions in solution

The solution is first acidified with nitric or hydrochloric acid
The barium chloride solution is added to the solution under test and if sulfate is present a white precipitate of barium sulfate is formed

Question 48

what are the solubilities of the sulfates

Answer 48

MgSO4 - soluble

CaSO4 - slightly soluble

SrSO4 - insoluble

BaSO4 - insoluble

Question 49

what are group 7 elements

Answer 49

group 7 on the right - hand side of the Periodic Table

• it is made up of non -metals
• as elements they exist as diatomic molecules F2, Cl2, Br2 and I2 called the halogens

Question 50

what are the physical properties of group 7

Answer 50

gaseous halogens vary in appearance

e.g.

Fluorine appears clear/ pale yellow gas

Chlorine - a greenish gas

Bromine - a red-brown liquid

iodine - a black solid

they get darker and denser going down the group

they all have a characteristic “swimming - bath” smell

Question 51

why are a number of fluorines properties untypical

Answer 51

• many of these untypical properties stem from the fact that the F - F bond is unexpectedly weak, compared with the trend fo the rest of the halogen

this is because the small size of the fluorine atom leads to repulsion between non - bonding electrons because they are so close

Question 52

what is the reactivity of the halogens

Answer 52

F - very reactive, toxic

Cl - very reactive, toxic

Br - very reactive, toxic

I grey crystals, reactive, toxic

Question 53

what are the clear trends in the halogens

Answer 53

the size of the atom increases as it goes down

the electronegativity of an atom decreases as it goes down

the melting points increases as it goes down

the boiling points increases as it goes down

Question 54

why does the atom get larger as it goes down a group

Answer 54

atoms get bigger going down the group because each element has one extra filled main level of electrons compared with one above it

Question 55

what is electronegativity

Answer 55

electronegativity is a measure of the ability of an atom to attract electrons, or electron density, towards itself within a covalent bond

Question 56

what does electronegativity depend on

Answer 56

electronengativity depends on the attraction between the nucleus and bonding electrons in the outer shell

This in turn, depends on a balance between the number of protons in the nucleus (nuclear charge) and the distance between the nucleus and the bonding electrons plus the shielding effect of inner shells off electrons

Question 57

what do the shared electrons in hydrogen halides do

Answer 57

the shared electrons in the H-X bond get further away from the nucleus as the atoms get larger going down the group

This makes the shared electrons further from the halogens nucleus and increases the shielding by more inner shells of electrons

Question 58

why do the melting and boiling points increases going down group 7

Answer 58

increases as you go down the group
This is because larger atoms have more electrons and this makes the van der Waals forces between the molecules stronger

Question 59

the lower the boiling point …

Answer 59

the lower the boiling point, the more volatile the element

So chlorine which is a gas at room temperature is more volatile than iodine which is a solid

Question 60

what are the trend in oxidising ability in the halogens

Answer 60

usually react by gaining electrons to become negative ions with a charge of -1

reactions are redox reactions - halogens are oxidising agents known

Question 61

what are displacement reactions

Answer 61

halogens will react with metal halides in solution in such away that the halide in the compound will be displaced by a more reactive halogen but not by a less reactive

this is called a displacement reaction

Question 62

give an example of a displacement reaction

Answer 62

e.g. chlorine will displace bromide ions, but iodine will not

in this redox reaction the chlorine is acting as an oxidising agent, by removing electrons from Br- and oxidising 2Br- to Br2 (the oxidation number of the bromine increases from -1 to 0)

Question 63

why can you not investigate fluorine in an aqueous solution

Answer 63

because it reacts with water

Question 64

how can you extract bromine from seawater

Answer 64

the oxidation of a halide by a halogen is the basis of a method for extracting bromine from seawater

seawater contains small amounts of bromide ions which can be oxidised by chlorine to produce bromine:

Cl2(aq) + 2Br-(aq) - Br2(aq) +2Cl-

Question 65

ho do we extract iodine from kelp

Answer 65

iodine was discovered in 1811

It was extracted from kelp, which is obtained by burning seaweed

Some iodine is still produced in this way
Salts such as sodium chloride, potassium chloride, and potassium chloride and potassium sulfate are removed from the kelp by washing wit water
The residue is then heated with manganese dioxide and concentrated sulfuric and iodine is liberated

2I- +MnO2 +4H+ - Mn2+ +2H2O +I2

Question 66

what are halide ions

Answer 66

halide ions can act as reducing agents
these reactions the halide ions (give away) electrons and become halogens molecules

Question 67

what is the trend in reducing ability of the halides

Answer 67

it is linked to the size of the ions

the bigger the ion, the more easily it loses an electron

This is because the electron is lost from the outer shell which is further from the nucleus as the ion gest larger so the attraction to the outer electron is less

This trend can be seen in the reactions of solid
Sodium halides with concentrated sulfuric acid

Question 68

how does sodium halides react with concentrated sulfuric acid

Answer 68

the products are all different and reflect the reducing powers of the halides ions shown above

Question 69

how does sodium chloride react with concentrated sulfuric acid

Answer 69

in this reaction, drops of concentrated sulfuric acid are added to solid sodium chloride

steamy fumes of hydrogen chloride are seen
the solid product is sodium hydrogensulfate

the reaction is:
NaCl(s) + H2SO4 - NaHSO4(s) + HCl(g)

This is not a redox reaction because no oxidation state has changed
The chloride ion is too weak a reducing agent to reduce the sulfur (oxidation state = +6) in the sulfuric acid

this reaction can be used to prepare hydrogen chloride gas which, because of this reaction was once called a salt gas

similar reaction with sodium fluoride - the fluoride ion is an even weaker reducing agent than the chloride ion

Question 70

how does sodium bromide react with concentrated sulfuric acid

Answer 70

you will see steamy fumes of hydrogen bromide and brown fumes of bromine
- colourless sulfur dioxide is also formed

Two reactions occur
first sodium hydrogen sulfate and hydrogen bromide are produced (in a similar acid- base reaction to sodium chloride)
NaBr(s) +H2SO4(l) - NaHSO4(s) +HBr(g)

However, bromide ions are strong enough reducig agents to reduce the sulfur acid to sulfur dioxide

The oxidation sate of the sulfur is reduced from +6 to +4 and that of bromine increases from - 1 to 0

This is a REDOX reaction
the reactions are exothermic and some of the bromine vaporiese

Question 71

how does sodium iodine react with concentrated sulfuric acid

Answer 71

you see steamy fumes of hydrogen iodine, the black solid of iodine, and the bad egg smell of hydrogen sulfide

Yellow solid sulfur may also be seen
colourless sulfur dioxide is also evolved

SEVERAL REACTIONS OCCUR:

• hydrogen iodine is produced in an acid - base reaction as before
• iodine ions are better reducing agents than bromide ions so they reduce the sulfur in sulfuric acid even further (from +6 to 0 and -2) so that sulfur dioxide, sulfur and hydrogen sulfide gas are produced

during the reduction from +6 to -2, the sulfur passes through oxidation state 0 and some yellow, solid sulfur may be seen

Question 72

how do we identify metal halides with silver ions

Answer 72

all metal halides (except fluorides) react with silver ions in an aqueous solution e.g. in silver nitrate

to form a precipitate of the insoluble silver halide
- silver fluoride does not form a precipitate because it is soluble in water

1. Dilute nitric acid HNO3 or (H+ aq) + NO-3(aq) is first added to the halide solution to get rid of any soluble carbonate CO2-(aq) or hydroxide OH- impurities
   - these would interfere with the test by forming insoluble silver carbonate
2. then add a few drops of silver nitrate solution and the halide precipitate forms

Question 73

why is the test useful for finding halide ions

Answer 73

the reaction can be used as a test for halides because you can tell from the colour of the precipitate which halide has formed

The colours of silver bromide and silver iodide are similar but if you add a few drops of concentrated ammonia solution, silver bromide dissolves but silver iodide does not

Question 74

what are the halide precipitates

Answer 74

silver fluoride - no precipitate

SILVER CHLORIDE - white precipitate
dissolves in dilute ammonia

SILVER BROMIDE - cream ppt
dissolves in concentrated ammonia

SILVER IODIDE - pale yellow ppt
insoluble i concentrated ammonia

Question 75

why do we extract titanium

Answer 75

titanium is a very useful metal because it is:

• abundant
• has a low density
• is corrosion resistant

It is useful for making strong, light alloys for use in aircraft for example

Question 76

how is titanium extracted

Answer 76

titanium is extracted by reaction with a more reactive metal (e.g. Mg)

steps in extracting titanium:

1. TiO2 (Solid) is converted to TiCl4 (liquid) at 900C
2. The TiCl4 is purified by fractional distillation in an argon atmosphere
3. The Ti is extracted by Mg in an argon atmosphere at 500C

Question 77

why is titanium expensive

Answer 77

the expensive cost of the Mg

This is a batch process which makes it expensive because the process is slower (having to fill up and empty reactors take time) and requires more labour and the energy is lost when the reactor is cooled down after stopping

3. the process is also expensive due to the argon, and the need to remove moisture (because TiCl4 is susceptible to hydrolysis)
4. high temperature required in both steps

Question 78

displacement of halides

Answer 78

potassium chloride & chloride - very pale green solution, no reaction

potassium bromide & chlorine - yellow solution, Cl has displaced Br

potassium iodide &chlorie - brown solution CL has displaced I

Question 79

what is the colour of the solution after a displacement reaction occurred

Answer 79

the colour of the solution in the test tube shows which free halogen is presented in solution

Chlorine - very pale green solution (often colourless)

Bromine = yellow solution

Iodine = brown solution (sometimes a black solid is present)

Question 80

how do you make bleach

Answer 80

if you mix bleach with cold, dilute sodium hydroxide solution at room temperature, you get sodium chlorate(I) solution (NaClO)

this is a common household bleach that kills bacteria

Question 81

what is the reaction between cold dilute sodium hydroxide and chlorine gas called

Answer 81

it is called disproportionation

this is because in the reaction chlorine is both oxidised and reduced

Question 82

write the reaction between dilute sodium hydroxide and Chlorine gas

Answer 82

2NaOH + Cl₂ → NaClO + NaCl + H₂O

ClO^{- is the chlorate (I) ion}

^{Chlorine’s oxidation state is +1 in this ion}

^{In NaCl the chlorine oxidation state is -1}

Question 83

what happens when we mix chlorine with water

Answer 83

when you mix chlorine with water, it undergoes disproportionation

You end up with a mixture of chloride ions and chlorate (I) ions

Question 84

write the equation that occurs between water and chlorine

Answer 84

Cl₂ + H₂O ⇔ 2H⁺ + Cl^- + ClO^-

Question 85

What happens when chlorine reacts with water in sunlight

Answer 85

Cl2 + H2O ⇔ 2H+ + Cl- + ½O₂

Question 86

why is it good to add chlorine to drinking water

Answer 86

chlorate ions kill bacteria so adding chlorine or a compound that contains chlorate ions to water can make it safe to drink or swim in it

it kills disease-causing microorganisms

it prevents the growth of algae, eliminating bad tastes and smells, and removes discolouration caused by organic compounds

however there are risks to using chlorine to treat water - chlorine gas is very harmful when breathed in - it irritates the respiratory system

Question 87

why do we still use chlorine to treat water

Answer 87

the benefits outweigh the negatives/ the risks