NEET Exam  >  NEET Notes  >  Chemistry Class 11  >  Characteristics of Compounds of the Alkali Metals

Characteristics of Compounds of the Alkali Metals | Chemistry Class 11 - NEET PDF Download

Characteristics of the Compounds of the Alkali Metals

All alkali metals form various oxides, hydroxides, carbonates and nitrates. They are hence, known as the most reactive elements as they have the weakest nuclear charge in the respective period. They have the tendency to lose their one valence electron in the last shell and form strong ionic bonds with their anions. Let’s, one by one study the characteristics of the compound of the alkali metals.

1. Forming Oxides and Hydroxides
The property of alkali metals allows their oxides, their peroxides and their super-oxides to dissolve in water quite readily. Such dissolving in water produces corresponding hydroxides which are basically very strong alkalis. Certain examples in the form of a chemical equation that display such phenomenon are as follows:

  • 2Na + 2H2O → 2NaOH + H2
  • Na2O + 2H2O→ 2NaOH
  • Na2O2 + 2H2O → 2NaOH + H2O2
  • 2KO2 + 2H2O → 2KOH + H2O2 + O2

It will be right to say that peroxides and super-oxides act as oxidising agents since they are able to react with water to form hydrogen oxide and oxygen easily. For any hydroxide of an alkali metal, one can observe whitish crystalline solids. As a base, they are very strong and can easily dissolve in water, also emitting a large quantity of heat in the process.
Moving down the periodic table, we can observe that the basic strength of such hydroxides, tends to increase. The hydroxides of alkali metals usually behave as strong bases owing to their low ionization energies which go down in the group. This decrease in ionization energies usually leads to the weakening of the bond between the metal and hydroxide ions and M – O bond in M – O – H can easily break, hence giving M+ and OH
This ultimately results in increased concentration of hydroxyl ions in the solution which can be defined by the increase in basic characters. All such hydroxides are very soluble in water and thermally stable with the exception of lithium hydroxide. Alkali metals with their hydroxides, being strongly basic, tend to react with all acids, leading to the formation of salts.

2. Forming Halides
Characteristics of Compounds of the Alkali Metals | Chemistry Class 11 - NEETThe alkali metals tend to combine directly with different halogens under appropriate conditions, thus forming halides of the general formula MX. Examples that demonstrate the formation of such halides are as follows:

  • M2O + 2HX → 2MX + H2O
  • MOH + HX → MX + H2O
  • M2CO3 + 2HX → 2MX + CO2 + H2O

(where M = Li, Na, K, Rb or Cs and X = F, Cl, Br or I). All of these halides are usually colourless, are high melting crystalline solids that have high negative enthalpies of formation.

3. Other Compounds of the Alkali Metals

  • Sodium Bicarbonate
    A concentrated solution of sodium carbonate can absorb Carbon Dioxide to give sparingly soluble sodium bicarbonate. We can demonstrate this by the following chemical equation:
    Na2CO3 + CO2 + H2O → 2NaHCO3
    Quite sparingly, this happens to be soluble in water. When heated between 250°C and 300°C, it gets converted into pure anhydrous sodium carbonate which can be later used for standardising acids.
  • Sodium Chloride
    We usually call it as ‘common salt’ that occurs abundantly in nature as a rock salt or halite. The most abundant source of Sodium Chloride is sea water where sodium chloride occurs to the extent of 3 percent. The sea water is exposed to the sun and air in large shallow pits.
    The gradual evaporation of water leads to the crystallization of the salt. The solution is later saturated with a current of dry hydrogen chloride whereby crystals of pure sodium chloride separate out in the process. Sodium Chloride is a colourless crystalline salt that is almost insoluble in alcohol but highly soluble in water.
  • Potassium Chloride
    It is prepared from fused carnallite that is nearly pure Potassium Chloride, separated from the melt, leaving fused MgCl2 behind. The salt is colourless in cubic crystal-like solid soluble in water. Its solubility increases in linear proportion with the temperature.
  • Potassium Sulphate
    We can obtain it by strongly heating potassium chloride with concentrated Sulphuric acid. It is a colourless crystalline salt, and it is less soluble in water than sodium sulphate.

Solved Question
Q. Why does lithium form only lithium oxide and not peroxide or superoxide?
Ans: 
Due to the small size of lithium compounds, the element has a strong positive field around it. When combined with the oxide anion (O2–), the positive field around the lithium-ion restricts the spreading movement of the negative charge towards another oxygen atom and thus prevents the formation of higher oxides. This is why lithium does not form lithium peroxide or lithium superoxide and gets restricted to only lithium oxide.

The document Characteristics of Compounds of the Alkali Metals | Chemistry Class 11 - NEET is a part of the NEET Course Chemistry Class 11.
All you need of NEET at this link: NEET
195 videos|337 docs|190 tests

FAQs on Characteristics of Compounds of the Alkali Metals - Chemistry Class 11 - NEET

1. What are the common characteristics of compounds of the alkali metals?
Ans. Compounds of the alkali metals, such as sodium and potassium, share certain common characteristics. These include high solubility in water, tendency to form ionic compounds, and the ability to easily lose their outermost electron to form positive ions.
2. What types of compounds do alkali metals typically form?
Ans. Alkali metals typically form ionic compounds, where they lose their outermost electron to form positively charged ions. These ions then combine with negatively charged ions, such as halides (e.g., chloride, bromide), oxides, or carbonates, to form compounds.
3. How does the solubility of alkali metal compounds in water contribute to their reactivity?
Ans. The high solubility of alkali metal compounds in water contributes to their reactivity by allowing them to readily dissociate into ions. This increases the chances of chemical reactions occurring and facilitates their participation in various chemical processes, such as ion exchange or precipitation reactions.
4. Why are alkali metal compounds often used as catalysts in chemical reactions?
Ans. Alkali metal compounds are often used as catalysts in chemical reactions due to their ability to increase the rate of reaction without being consumed in the process. Their high reactivity and propensity to form positive ions make them effective catalysts for various chemical transformations.
5. How do alkali metal compounds contribute to the vibrant colors observed in fireworks?
Ans. Alkali metal compounds are responsible for the vibrant colors observed in fireworks. When these compounds are heated, the alkali metal ions present in them get excited to higher energy levels. As they return to their ground state, they release energy in the form of light, producing characteristic colors. For example, sodium compounds produce a yellow color, while potassium compounds produce a violet color.
195 videos|337 docs|190 tests
Download as PDF
Explore Courses for NEET exam

How to Prepare for NEET

Read our guide to prepare for NEET which is created by Toppers & the best Teachers
Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev
Download the FREE EduRev App
Track your progress, build streaks, highlight & save important lessons and more!
Related Searches

pdf

,

past year papers

,

Characteristics of Compounds of the Alkali Metals | Chemistry Class 11 - NEET

,

video lectures

,

practice quizzes

,

Characteristics of Compounds of the Alkali Metals | Chemistry Class 11 - NEET

,

Important questions

,

Extra Questions

,

shortcuts and tricks

,

Viva Questions

,

Previous Year Questions with Solutions

,

Free

,

ppt

,

Semester Notes

,

Characteristics of Compounds of the Alkali Metals | Chemistry Class 11 - NEET

,

study material

,

Exam

,

Summary

,

Objective type Questions

,

MCQs

,

Sample Paper

,

mock tests for examination

;