Group 1 Elements

Question 1

What are the elements in G1?

Answer 1

Li, Na, K, Rb, Cs, Fr

Question 2

Is Hydrogen a G1 element? Why?

Answer 2

No. It is there because it can lose an electron to become a hydrogen ion like the rest. It can also gain one like the halogens to form the hydride ion.

Question 3

What groups of the Periodic Table can hydrogen stay?

Answer 3

1 and 7

Question 4

What are the general characteristics of G1 elements?

Answer 4

• Very reactive, pure form impossible but extracted by electrolysis
• Melting and boiling points decrease down the group
• All metals
• Good reducing agents
• Highly electropositive

Question 5

What is the only stable nitride of G1?

Answer 5

Lithium nitride (Li3N). Group 2 typically form nitrides but Li is the only one that does it in G1.

Question 6

Why isn’t Li a typical G1 element?

Answer 6

It’s small size and large charge and hydration energy.

Question 7

What are the special properties of Li in G1?

Answer 7

• It is more covalent than the rest because of its high polarizing power
• It has the smallest atomic size and highest charge.

High Charge = High Polarizing power

Question 8

What are the uses of G1 elements?

Answer 8

• Li is used in the manufacture of small lifetime, rechargeable batteries.
• Na is a reducing agent and combines with other metals to form alloys
• KO2 is used for oxygen generators, mostly used by divers.

Question 9

Reactions with water

Answer 9

They react vigorously with water except Li which reacts slowly, to produce the corresponding hydroxide (strong and soluble) and H2. LiOH is only slightly soluble in water.

Question 10

Reactions with oxygen

Answer 10

They form ionic oxides which can dissolve in water to give alkaline solutions. Li oxidizes less rapidly than the rest because it is covalent.

Elements higher up the group form normal oxides but form peroxides in excess O2.

Elements lower down form superoxides. The formation of these oxides are exothermic.

Question 11

Reactions with hydrogen

Answer 11

They form ionic halides which are typically good reducing agents.

Question 12

What is the most important G1 hydride?

Answer 12

Lithium tetrahydridoaluminate or lithium aluminium hydride because it is used as a reducing agent in organic chem to reduce amides to amines.

Question 13

Who forms simple oxides, peroxides and superoxides?

Answer 13

Li and Na form simple oxides
Na and K form peroxides
K, Rb and Cs form superoxides

Question 14

What are the oxidation numbers of the types of oxides?

Answer 14

Simple - O-2
Peroxide - O2 (2-)
Superoxide - -1

Question 15

Reactions with Halogens

Answer 15

They form ionic halides.

Question 16

What are characteristics of the G1 halides?

Answer 16

Except Li (covalent), they are soluble in water.

Hydrohalic acids (like HCl) are prepared by reacting a metalic halide with strong sulphuric acid.

Question 17

What are the examples of oxosalts?

Answer 17

Sulphites, Nitrites, Nitrides, Carbonates, Bicarbonates, Sulphates

Question 18

G1 Carbonates

Answer 18

• M2Co3
• Ionic
• White solids at room temperature
• Decompose at above 1000 celsius to give oxide and CO2. No water vapour.

Question 19

G1 Bicarbonates

Answer 19

• All solids, except Li which exists in solution
• G1 are the only metals that form solid bicarbonates, except Li
• When they decompose, the carbonate, CO2 and water vapour are give off.

Question 20

What is the difference between G1 carbonates and bicarbonates?

Answer 20

On decomposition, the former gives an oxide and CO2. The latter gives water vapour, the carbonate and CO2.

Question 21

What are the uses of G1 carbonates?

Answer 21

• Na carbonate is used in soap making as a reducing agent

- They are used in fire extinguishers and baking soda because of how easily they give off CO2 on decomposition.

Question 22

Explain the thermal stability of G1 carbonates

Answer 22

• Carbonates are stable up to 1000 celsius
• They decompose to CO2 and the corresponding oxide ion on heating
• Carbonates of K, Rb and S are deliquescent
• Thermal stability increases down the group

Question 23

What is the most thermally unstable G1 carbonate?

Answer 23

Lithium (increases down the group)

Question 24

Describe the solubility of G1 carbonates in water

Answer 24

They are ionic so they are generally soluble in water, except for Li.

Question 25

What is the solubility in water trend for G1 carbonates?

Answer 25

It increases as you go down the group.

Question 26

What is the difference between nitrates and nitrites?

Answer 26

Nitrate = NaNO3
Nitrite = NaNO2

Question 27

What is the special property of nitrates?

Answer 27

They are all soluble

Question 28

What is the relationship between thermal stability and solubility in water of the nitrates?

Answer 28

They both increase with increase in atomic number.

Question 29

How is NaNO3 prepared?

Answer 29

By neutralizing HNO3 with Na2CO3. CO2 is released.

Question 30

What happens to G1 nitrates on heating?

Answer 30

They give off nitrites and O2.

Question 31

What are the uses of nitrates and nitrites?

Answer 31

NaNO3 is used as fertilizer. NaNO2 is used in the production of dyes and antioxidants (preservatives)

Question 32

What is the special feature of LiNO3?

Answer 32

On heating, it decomposes to the corresponding oxide, Nitrogen dioxide and O2.

Question 33

What are the sulphates, hydrogen sulphates and sulphites?

Answer 33

SO4, HSO4 and SO3 respectively.

Question 34

What do the sulphates and hydrogen sulphates have in common?

Answer 34

They are both soluble in water.

Question 35

Describe the reaction between sodium sulphite and acids.

Answer 35

On heating, it reacts with acids to liberate SO2 gas.

Question 36

What is the difference between sulphate and sulphite salts?

Answer 36

Sulphate salts do not give off any gas, Sulphite salts do.

Question 37

Which compound is formed in the reaction of sodium sulphite with powder S?

Answer 37

Sodium thiosulphate (Na2S2O3). It is useful in iodine titration and photography.