Topic 4: Inorganic Chemistry and the Periodic Table

Question 1

What is the trend for the ionisation energy down Group 2?

Answer 1

The first ionization energy of elements in Group 2 of the periodic table decreases as you move down the group.
This is because as you move down the group, more electron shells are added, which increases the atomic radius. This means the outermost shell is further away from the nucleus.
The shielding effect increases.
The presence of more inner electron shells containing electrons increases the shielding effect on the outermost electrons.
Attraction between nucleus and outermost electrons decreases,
The attraction between the outermost electrons and the nucleus decreases, so less energy is required to remove them.

Question 2

What is the trend of reactivity down the group of Group 2?

Answer 2

The reactivity of elements in Group 2 of the periodic table increases as you move down the group.
The atomic radius increases down the group, which means the outermost electrons are further from the nucleus and less attracted to it. This makes it easier for the electrons to be lost, making the atom more reactive.
The reactions of Group 2 elements with dilute hydrochloric acid become more vigorous as you move down the group. The reaction with water also becomes more vigorous, with the most reactive elements reacting very slowly and the least reactive elements reacting very vigorously.

Question 3

What is the reaction of the elements Mg to Ba in Group 2 with Oxygen, Chlorine and Water?

Answer 3

Group 2 elements react with oxygen to form oxides. The reactions are:
Magnesium: Burns easily in air with a bright white flame to form magnesium oxide (MgO). The equation for this reaction is 2Mg(s) + O2(g) → 2MgO(s).
Strontium: Forms strontium oxide (SrO) when heated in oxygen under high pressure, or strontium peroxide (SrO2) when heated in oxygen normally.
Barium: Forms barium oxide (BaO) when heated in oxygen normally, or barium peroxide (BaO2) when heated in oxygen normally.

Question 4

What is the reaction of the elements Mg to Ba in Group 2 with Chlorine?

Answer 4

When the elements magnesium (Mg) to barium (Ba) in Group 2 react with chlorine gas, they form metal chlorides, which are white precipitates:
Reaction: Mg (s) + Cl2 (g) → MgCl2 (s) During this reaction, chlorine is reduced and the metal is oxidized.

Question 5

What is the reaction of the elements Mg to Ba in Group 2 with Water?

Answer 5

Group 2 elements react with water to form metal hydroxides. The reactions are:
Magnesium: Reacts slowly with water to form magnesium hydroxide (Mg(OH)2) and hydrogen gas. Reacts vigorously with steam to form magnesium oxide (MgO).
Calcium: Reacts moderately with water to form calcium hydroxide (Ca(OH)2) and hydrogen gas.
Strontium: Reacts rapidly with water to form strontium hydroxide (Sr(OH)2) and hydrogen gas.
Barium: Reacts vigorously with water to form barium hydroxide (Ba(OH)2) and hydrogen gas.

Question 6

How do oxides of Group 2 elements react with water?

Answer 6

Group 2 oxides react with water to form metal hydroxides and alkaline solutions. The general reaction is metal oxide plus water to form metal hydroxide: MO + H2O → MOH2.
The resulting solution is alkaline because the reaction releases hydroxide ions, OH–.
The solutions become more alkaline as you move down the group. This is because the hydroxides that form become more soluble, causing more hydroxide ions to dissociate into the solution.

Question 7

How do oxides of Group 2 elements react with dilute acid?

Answer 7

When Group 2 oxides react with dilute acids, they form a salt and water in a neutralization reaction:
Metal oxide + dilute hydrochloric acid: Forms metal chloride and water
Metal oxide + dilute sulfuric acid: Forms metal sulfate and water
The type of salt that forms depends on the acid used:
Hydrochloric acid: Forms chloride salts
Sulfuric acid: Forms sulfate salts
Nitric acid: Forms nitrate salts

Question 8

How do oxides of Group 2 elements react with their hydroxides with dilute acid?

Answer 8

Group 2 metal oxides and hydroxides react with dilute acids to form a salt and water, in a neutralization reaction:
Reaction with oxides: MO (s) + acid (aq) → salt (aq) + H2O (l)
Reaction with hydroxides: M(OH)2 (s) + acid (aq) → salt (aq) + 2H2O (l)
The salt formed depends on the acid used. For example, hydrochloric acid forms chloride salts.
Group 2 elements are oxidized from an oxidation state of 0 to +2, while hydrogen is reduced from a +1 state to 0. This makes the reaction between a Group 2 element and oxygen a redox reaction.

Question 9

What is the trends of solubility of the hydroxides in Group 2?

Answer 9

The solubility of Group 2 metal hydroxides increases as you move down the group, from magnesium to barium. The lattice energy of the hydroxide salt decreases as you move down the group.
Coordination number increases
The coordination number of the metal ion increases as you move down the group.
The radius of the metal cations increases as you move down the group.
Solutions become more alkaline
The solutions become more alkaline as you move down the group because the hydroxides dissociate in solution to give an excess of OH- ions.
For example, magnesium hydroxide has a solubility of 0.00064 g/100 mL at 25°C, while barium hydroxide has a solubility of 3.7 g/100 mL at the same temperature.

Question 10

What is the trends of solubility of the sulfates in Group 2?

Answer 10

The solubility of Group 2 sulfates decreases as you move down the group.
Magnesium sulfate: The most soluble Group 2 sulfate
Calcium sulfate: Sparingly soluble
Strontium sulfate: Less soluble than calcium sulfate
Barium sulfate: The least soluble Group 2 sulfate and is insoluble
This is because the sulfate ion is large, so larger cations form stronger ionic compounds.
Barium sulfate is used in medicine as a contrast medium in x-rays. It’s insoluble, so it moves through the digestive system without being absorbed and shows up dark on an x-ray.

Question 11

What is the reason for the trend in thermal stability of the nitrates in Group 1?

Answer 11

The thermal stability of nitrates in Group 1 increases down the group because smaller positive ions at the top of the group polarize the anions more than the larger ions at the bottom of the group.
The higher the charge and the smaller the ion, the higher the polarizing power. The more polarized the ions are, the more likely they are to thermally decompose as the bonds in the nitrate ions become weaker.
When heated, most nitrates decompose to give the metal oxide, brown fumes of nitrogen dioxide, and oxygen.

Question 12

What is the reason for the trend in thermal stability of the nitrates in Group 2?

Answer 12

The thermal stability of nitrates in Group 2 of the periodic table increases down the group because the polarizing effect of the cations decreases.
The ions of elements at the top of Group 2 are smaller and have a higher charge density than those at the bottom. This means that the smaller ions have a greater polarizing effect on the negative nitrate ions. The more polarized the anion is, the less heat is required to separate the two ions.
The decomposition of Group 2 nitrates involves the breakdown of the nitrate ion into metal nitrite and oxygen. The only difference between the nitrates is how much heat is required for the reaction to occur.

Question 13

What is the reason for the trend in thermal stability of the carbonates in Group 1?

Answer 13

The thermal stability of carbonates in Group 1 of the periodic table increases down the group because smaller, positively charged ions at the top of the group polarize the carbonate ions more than larger ions at the bottom.
The smaller the ion and the higher its charge, the more it polarizes the carbonate ion.
The more polarized the carbonate ion, the more likely it is to thermally decompose. This is because the bonds in the carbonate ion weaken.
Ionic radius
As you move down the group, the ionic radius increases for the same charge. This means that the smaller ions have a higher charge density.
The more polarized the carbonate ion, the less heat is required to separate the ions.

Question 14

What is the reason for the trend in thermal stability of the carbonates in Group 2?

Answer 14

The thermal stability of carbonates in Group 2 of the periodic table increases down the group because the positive ions get larger and have a lower charge density.
The larger positive ions at the bottom of the group have less of an effect on the carbonate ions around them.
Lower charge density
The larger ions have the same charge spread out over a larger volume, so their charge density is lower.
Smaller ions have a higher charge density and a greater polarizing effect on nearby negative ions.
More heat is required to break the bonds in the carbonate ions and separate them for thermal decomposition.

Question 15

What is the colour of each group 1 flame?

Answer 15

Li = red
Na = strong persistent yellow-orange
K = lilac (pink)
Rb = red (reddish-violet)
Cs = blue-violet (see below)
Ca = orange-red
Sr = red
Ba = pale green
Cu = blue-green (often with white flashes)
Pb = greyish-white

Question 16

What is the colour of each group 2 flame?

Answer 16

Lithium, Li+ = Red
Sodium, Na+ = Yellow
Potassium, K+ = Lilac
Calcium, Ca2+ = Orange-red
Barium, Ba2+ = Green
Copper, Cu2+ = Blue-green

Question 17

Why does the flame change colour?

Answer 17

Salts change the colour of a flame because the electrons in the metal ions are excited to higher energy levels by heat, and then release energy in the form of light as they return to their original state.

Question 18

How to show patterns in thermal decomposition of Group 1 nitrates?

Answer 18

The thermal stability of Group 1 nitrates increases as you move down the group. This is because the positive ions at the top of the group are smaller and have a higher charge, which polarizes the anions more. The more polarized the ions are, the weaker the bonds in the nitrate ions become, and the more likely they are to thermally decompose.
The decomposition of nitrates is endothermic, meaning that heat is required to break the chemical bonds in the molecule. The enthalpy changes for the decomposition of the various carbonates are all strongly endothermic, which means that the reactions are likely to need to be heated constantly to happen.
The general equation for the decomposition of Group 1 nitrates is: 4LiNO (s) → 2LiO (s) + 4NO (g) + O (g).

Question 19

How to show patterns in thermal decomposition of Group 2 nitrates?

Answer 19

The thermal stability of Group 2 nitrates increases as you move down the group. This is because the ions increase in size and the charge density decreases. The lower the charge density, the less the carbonate ion is distorted, and the more stable it is.
More heat is required to break down the nitrate ions as you move down the group.
When heated, Group 2 nitrates produce a metal oxide, oxygen, and nitrogen dioxide. The nitrate and oxide are both white solids, and nitrogen dioxide is a brown gas.
The general equation for the thermal decomposition of Group 2 nitrates is: 2X(NO3)2 → 2XO + 4NO2 + O2, where X is the Group 2 metal.

Question 20

How to show patterns in thermal decomposition of Group 1 carbonates?

Answer 20

Put a large amount of the carbonate in a test tube
Attach a delivery tube and clamp it so that the tube dips into a second test tube containing limewater
Gently heat the solid at first, then more strongly
Remove the delivery tube from the limewater before or as soon as you stop heating
Record your observations, including what happens to the limewater, if the solid melts, and if there are any color changes
Group 1 carbonates: Most Group 1 carbonates are thermally stable, except for lithium carbonate (Li2CO3), which decomposes when heated.
Polarizing effect: The polarizing effect is reduced when the positive ion only has one positive charge. This means that Group 1 compounds are more thermally stable than Group 2 compounds.

Question 21

How to show patterns in thermal decomposition of Group 2 carbonates?

Answer 21

As you move down Group 2, more heat is required to break down the carbonates. This is because the ions increase in size and the carbonates increase in thermal stability.
Some thermal decomposition reactions produce a color change. For example, when copper carbonate is heated, it breaks down to produce copper oxide and carbon dioxide, and you can see a color change from green to black.
You can use limewater to detect the carbon dioxide produced. Limewater turns from clear to cloudy when it comes into contact with carbon dioxide.

Question 22

What is the trend in melting and boiling point for Group 7 elements?

Answer 22

The melting and boiling points of the elements in Group 7 increase as you move down the group.
This is because the molecules of the halogens become larger as you move down the group, which increases the intermolecular forces between them. More energy is required to break these forces, which is why the melting and boiling points increase.

Question 23

What is the trend in physical state for Group 7 elements?

Answer 23

The physical state of the elements in Group 7 of the periodic table changes as you move down the group:
At room temperature
At 20°C, fluorine and chlorine are gases, bromine is a liquid, and iodine is a crumbly solid.

Question 24

What is the trend in electronegativity for Group 7 elements?

Answer 24

In Edexcel A Level Chemistry, the trend in electronegativity for Group 7 elements is that it decreases as you move down the group.
Electronegativity is the tendency of an atom to attract electrons when forming a chemical bond. As you move down Group 7, the atomic radius of the elements increases, which means the outer shell gets further from the nucleus. This results in more shielding by inner shell electrons, and the incoming electrons are further away from the nucleus. The increased shielding outweighs the effect of the increasing nuclear charge, so electronegativity decreases.

Question 25

What is the trend of reactivity of Group 7 elements?

Answer 25

The reactivity of Group 7 elements decreases as you move down the group.
As you move down the group, the number of electron shells increases, and the distance between the nucleus and the outer electron increases. This means that the force of attraction between the nucleus and the outer electron decreases, making it harder for the atoms to gain electrons.
Group 7 elements are all reactive non-metals that react with metals to form metal halides, and with hydrogen to form acidic hydrogen halides. Fluorine is the most reactive because it is the smallest halogen, and its outermost shell is closest to the nucleus.

Question 26

What is the trend of reactivity of Group 7 in terms of redox reactions of Cl2, Br2 and I2?

Answer 26

The order of reactivity is chlorine > bromine > iodine. This is because chlorine could displace bromine and iodine, bromine could only displace iodine, but iodine could not displace chlorine or bromine.

Question 27

What is the trend of reactivity of Group 7 in terms of redox reactions of halide ions in aqueous solutions?

Answer 27

The group 7 elements are all reactive non-metals. They react with metals to form metal halides, and with hydrogen to form acidic hydrogen halides. Reactivity decreases down the group.

Question 28

In terms of changes in oxidation number, how do halogens react with Group 1 in an oxidation reaction?

Answer 28

In an oxidation reaction with halogens, Group 1 metals are oxidized from an oxidation state of 0 to 1+.
Sodium and chlorine
2Na (s) + Cl2 (g) → 2NaCl (s)
Na changes from 0 to +1
Halogens are oxidizing agents, meaning they remove electrons from metals, causing the metal’s oxidation number to increase. In the process, the halogens gain electrons and become reduced, causing their oxidation number to decrease.

Question 29

In terms of changes in oxidation number, how do halogens react with Group 2 in an oxidation reaction?

Answer 29

In an oxidation reaction with a halogen, Group 2 metals change from an oxidation state of 0 to an oxidation state of +2.
Halogens react with Group 2 metals to form halide salts, which are ionic compounds. In these reactions, the halogens act as oxidizing agents, causing the metals to be oxidized.
When calcium (a Group 2 metal) reacts with bromine, the oxidation number of calcium changes from 0 to +2.

Question 30

In terms of changes in oxidation number, the disproportion reaction of chlorine with water

Answer 30

In the disproportionation reaction of chlorine with water, the oxidation number of chlorine changes from 0 in Cl2 to +1 in ClO- and -1 in Cl-.
A disproportionation reaction is a redox reaction where one compound is both oxidized and reduced, resulting in two compounds with different oxidation states. In the case of chlorine and water, the chlorine is oxidized to form chlorate(I) ions (ClO-) and reduced to form chloride ions (Cl-).
The balanced chemical equation for this reaction is: Cl2(g)+2NaOH(aq) = NaCl(aq)+NaClO(aq)+H2O(l)
Chlorine can also react with water to form hydrochloric acid (HCl) and hypochlorous acid (HOCl). Hypochlorous acid is a weak but strong oxidizing acid that gives chlorine its bleaching properties.

Question 31

In terms of changes in oxidation number, the disproportion reaction of chlorine with cold, dliute aqueous sodium hydroxide to form bleach

Answer 31

In the disproportionation reaction of chlorine with cold, dilute aqueous sodium hydroxide to form bleach, chlorine’s oxidation number changes from 0 to +1 and -1.
The balanced chemical equation for this reaction is: Cl₂ (g) + 2NaOH (aq) → NaCl (aq) + NaClO (aq) + H₂O (l). In this reaction, chlorine is both oxidized and reduced:
Oxidized: Chlorine’s oxidation state increases from 0 in Cl₂ to +1 in NaClO.
Reduced: Chlorine’s oxidation state decreases to -1 in NaCl.
This is an example of a disproportionation reaction, which occurs when a single substance is both oxidized and reduced.

Question 32

In terms of changes in oxidation number, the disproportion reaction of chlorine with a hot alkali

Answer 32

In the disproportionation reaction of chlorine with a hot alkali, chlorine is both oxidized and reduced, resulting in changes in oxidation number.
Cl₂ = 0 in Cl₂
NaClO = +1 in NaClO
NaCl = -1 in NaCl
The balanced chemical equation for the reaction of chlorine with hot sodium hydroxide is: Cl2(g)+2NaOH(aq) = NaCl(aq)+NaClO(aq)+H2O(l)
Thus making it a disproportion reaction.

Question 33

The reaction between solid Group 1 halides with concentrated sulfuric acid to show the trend in the reducing ability of hydrogen halides

Answer 33

Concentrated sulfuric acid
Chloride, bromide and iodide ions react with concentrated sulfuric acid to produce toxic gases
These reactions should therefore be carried out in a fume cupboard
The general reaction of the halide ions with concentrated sulfuric acid is:
H2SO4(aq) + X-(aq) → HX(g) + HSO4-(aq)

(general equation)

Where X- is the halide ion

Reaction of chloride ions with concentrated sulfuric Acid
Concentrated sulfuric acid is dropwise added to sodium chloride crystals to produce hydrogen chloride gas
The reaction that takes place is:
H2SO4 (aq) + NaCl (s) → HCl (g) + NaHSO4 (s)

The HCl gas produces is seen as white fumes

Question 34

What is the precipitation reactions of the aqueous anions?

Answer 34

Cl- + AgNo3 = White precipitate (AgCl)
Br- + AgNo3 = Cream precipitate (AgBr)
I- + AgNo3 = Yellow precipitate (AgI)
Cl- + dilute NH3 = Precipitate dissolves
Br- + dilute NH3 = Cream precipitate (AgBr)
I- + dilute NH3 = Yellow precipitate (AgI)
Cl- + conc NH3 = Precipitate dissolves
Br- + conc NH3 = Precipitate dissolves
I- + conc NH3 = Yellow precipitate (AgI)

Question 35

What is the reaction of hydrogen halides with ammonia and with water?

Answer 35

Hydrogen halides react with ammonia gas to form ​ammonium salts​. The hydrogen halides (hydrogen chloride, hydrogen bromide and hydrogen iodide) are strong acids in solution and react with ammonia in an​ acid-base reaction​to form a salt. Example: Hydrogen halides react with water to form ​dilute acids​.

Question 36

Make a prediction about fluorine and astatine in terms of its trends

Answer 36

Melting and boiling points increase as you go down since more intermolecular Van de van forces (London forces) with increasing Ar (relative atomic mass). Fluorine would be a gas at room temperature and astatine would be a solid at room temperature

Question 37

What reaction identifies carbonate ions and hydrogencarbonate ions using an aqueous acid to form carbon dioxide?

Answer 37

When a dilute acid, like hydrochloric acid, is added to a carbonate, carbon dioxide CO2 is produced, causing fizzing. To confirm the presence of CO2, bubble it through limewater CaOH2, which will turn cloudy or milky white due to the formation of calcium carbonate CaCO3.
The reaction between hydrochloric acid HCl and hydrogencarbonate ions HCO3- produces carbon dioxide CO2, water H2O, and sodium chloride NaCl.

Question 38

What reaction identifies sulfate ions using acidified barium chloride?

Answer 38

A displacement reaction that forms a white precipitate of barium sulfate:
Acidify the sample with dilute hydrochloric acid (HCl)
Add a few drops of barium chloride solution
A white precipitate of barium sulfate forms if sulfate ions are present
The equation for this reaction is Ba2+ (aq) + SO42- (aq) → BaSO4 (s).
The hydrochloric acid removes any traces of carbonate ions, which would otherwise give an incorrect positive result.

Question 39

What reaction identifies ammonium ions using sodium hydroxide solution?

Answer 39

Add a few drops of dilute sodium hydroxide solution to the sample
Gently warm the sample
If ammonium ions are present, ammonia gas will be produced
Test the gas with damp red litmus paper
If the litmus paper turns blue, ammonium ions are present
Ammonia gas has a distinct choking odor and turns damp red litmus paper and damp universal indicator paper blue.