Skip to content
Related Articles

Related Articles

Improve Article
Save Article
Like Article

Biological Importance of Alkali and Alkaline Earth Metals

  • Last Updated : 02 Dec, 2021

Elements are arranged in a periodic table row-wise and column-wise according to similarities in their chemical and physical properties. The elements in the first column are known as Group 1 elements which have the following elements lithium, sodium, potassium, rubidium, Caesium and Francium. All these elements have similar properties except Lithium so all the elements of this group including lithium (yet it has different properties ) are known as Alkali Metals

The elements in the second column are known as Group 2 elements which have the following elements beryllium, magnesium, calcium, strontium, barium and radium. All these elements have similar properties except Beryllium so all the elements of this group except beryllium are known as Alkaline Earth Metals.

Common Characteristics of Alkali Metals  

  • Atomic Radii: In the periodic table, the atomic radii of elements decreases as we move from left to right in a row while in a column the atomic radii increases as we move from top to bottom. Hence atomic radii of alkali metals increase down the column from Lithium to Francium.
  • Ionization Energy: Ionization energy or ionization enthalpy is the minimum amount of energy needed to remove electrons from the energy shells of an atom. Alkali metals have low ionization energies because atoms of alkali metals have a big size due to which the nuclear charge of an atom can be outweighed so it is difficult to take out an electron from an energy shell. The trend of ionization energies is opposite to atomic radii so ionization energies decrease as we move down the group.
  • Electronegativity: Whenever an atom of an element forms a bond with an atom of some other element by sharing electron pairs then every atom tries to attract shared electron pair towards itself, this tends to attract shared pair of electrons is known as Electronegativity. Electronegativity of alkali metals decreases down the group.
  • Hydration Energy: Hydration energy is the amount of energy released on the hydration of one mole of ions. Hydration energy of alkali metals follows the opposite trend as that of atomic size means hydration enthalpy of ions decreases down the group as atomic size increases.

Li+ > Na+ > K+ > Rb+ > Cs+

Physical Properties of Alkali Metals:

  1. Appearance of alkali metals is silvery white.
  2. These are soft metals.
  3. They have a lower boiling point than alkaline earth metals.
  4. These elements can be tested by flame test as they give different colours on being exposed to flame.
  5. These metals can conduct electricity.
  6. Alkali metals have low densities, they are light metals.

Uses of Alkali Metals:

  1. Lithium is used in making different types of alloys one is known as white metal.
  2. Lithium is also used in storing energy in electrochemical cells.
  3. In photoelectric cells, Caesium is used as an electrode.
  4. Potassium is mainly used in fertilizers, insecticides and pesticides.
  5. Sodium especially liquid sodium can be used in nuclear reactors as coolants.

Biological Importance of Alkali Metals

Alkali metals react readily with air and water so to avoid any reaction these metals should be stored under some kind of oil. All the alkali metals play a very important role in the existence and maintenance of the life cycle. Let’s see the biological importance of all alkali metals one by one.

  1. Biological Importance of Lithium: Lithium is important to humans through its high concentration has a toxic effect it naturally occurs in soil and hence with included in the food chain, talking about biological importance so it has an antioxidant effect and many medicines which are used to treat depression and anxiety disorders uses lithium compounds. Lithium chloride is used to treat hypertension.
  2. Biological Importance of Sodium: Sodium plays a very important role in balancing water in the human body and sodium ions are used to transmit nerve impulses, these sodium ions are also responsible for muscle contraction and relaxation. A sufficient amount of sodium in the body helps to prevent the body from different failures like kidney failure, heart failure etc.
  3. Biological Importance of Potassium: Potassium is very important as it maintains osmotic pressure between cells and interstitial fluid, it is used to treat many diseases like hypokalemia, weakness of muscles, cardiac disorders etc. Potassium ions help the nutrients of food to move inside cells and move waste products outside the cells.
  4. Biological Importance of Rubidium: Rubidium helps in the stimulation of metabolism. Some isotopes of rubidium are used in the treatment of severe heart diseases. Rubidium ions are also found in muscles.
  5. Biological Importance of Caesium: Chemical properties of caesium are mostly similar to that of potassium so in the body caesium can replace potassium which is very harmful so caesium ions are mostly avoided by humans.
  6. Biological Importance of Francium: Actually francium does not have any biological role as such.

Common Characteristics of Alkaline Earth Metals

  • Atomic Radii: In the periodic table, the atomic radii of elements decreases as we move from left to right in a row while in a column the atomic radii increases as we move from top to bottom. Hence atomic radii of alkaline earth metals increase down the column also when compared with alkali metals the size of alkaline earth metals are smaller because the nuclear charge of these elements is more than alkali metals. 

 Be< Mg< Ca< Sr< Ba< Ra

  • Ionization Energy: Ionization energy or ionization enthalpy is the minimum amount of energy needed to remove electrons from the energy shells of an atom. Alkaline earth metals have low ionization energies because atoms of alkaline earth metals have a big size due to which it is difficult to take out electrons from the energy shell. The trend of ionization energies is opposite to atomic radii so ionization energies decrease as we move down the group.

Be> Mg> Ca> Sr> Ba> Ra

  • Electronegativity: Whenever an atom of an element forms a bond with an atom of some other element by sharing electron pairs then every atom tries to attract shared electron pair towards itself, this tends to attract shared pair of electrons is known as Electronegativity. Electronegativity of alkaline earth metals decreases down the group.

Be> Mg> Ca> Sr> Ba> Ra

  • Hydration Energy: Hydration energy is the amount of energy released on the hydration of one mole of ions. Hydration energy of alkaline earth metals follows the opposite trend as that of atomic size means hydration enthalpy of ions decreases down the group as atomic size increases. 

Be> Mg> Ca> Sr> Ba> Ra

Physical Properties of Alkaline Earth Metals:

  1. The appearance of alkaline earth metals is silvery white.
  2. These are soft metals.
  3. They have a higher boiling point than alkali metals.
  4. These elements can be tested by flame test as they give different colours on being exposed to flame.
  5. These metals can conduct electricity.
  6. Alkaline earth metals have high electropositivity so their nature is electropositive.
  7. Among alkaline earth metals, magnesium does not give any colour on being exposed to flame.
  8. Alkaline earth metals are good conductors of heat.
  9. The density of alkaline earth metals is greater than those of alkali metals.
  10. Among alkaline earth metals, the density of calcium is the lowest.
  11. These metals are soluble in water. 

ses of Alkaline Earth Metals:

  1. Magnesium is used in making different types of alloys.
  2. Magnesium is also used in medicines to take antacids.
  3. Radium is used for the treatment of cancer.
  4. Calcium is used in the extraction of different elements.
  5. Barium is used in removing air from vacuum tubes.
  6. Calcium is used to make calcium carbonate which is used to make different products like chalk, marble, limestone etc.
  7. Alkaline earth metals release hydrogen gas when react with acids, this hydrogen gas can be used for other purposes.  
  8. Alkaline earth metals are used in making electro-chemical and photoelectric cells.
  9. Alloys of magnesium are used in the manufacturing of air crafts and fighter planes.
  10. Plaster of Paris is also formed from calcium and is used in decorations, designing and fireproofing.

Biological Importance of Alkaline Earth Metals

Alkaline earth metals are of great importance to both animal life as well as for plant life, these elements play more than one role in chemical and biological processes. Let’s see the biological importance of all alkaline earth metals one by one.

  1. Biological Importance of Beryllium: Beryllium is used in blood samples to detect HIV and other diseases. It is also used in X-Ray experiments to make radiation windows. Beryllium mammography is a technique used to detect tumours and breast cancers.
  2. Biological Importance of Magnesium: Magnesium helps in the synthesis of proteins and the growth of cells. It plays a vital role in muscles movement and blood pressure. Magnesium provides strength to bones and teeth, it helps to cure asthma and other lung diseases. It also prevents the blood from clotting.
  3. Biological Importance of Calcium: Calcium is necessary for the strengthening of bones, it also forms cell walls and helps in the clotting of blood in case of injury. Calcium keeps the body strong and healthy.
  4. Biological Importance of Strontium: Strontium is mainly used in bones restoration as it promotes the uptake of calcium and helps in fixing cracked or broken bones by using calcium and strontium interactions. 
  5. Biological Importance of Barium: Barium is not biologically important to humans as it has toxic effects, a small amount of barium solution can cause breathing problems and it increases the heart rate and blood pressure. There is a chance of kidney and heart damage if barium is consumed.
  6. Biological Importance of Radium: Radium is radioactive and due to its toxicity there is not much biological use of Radium.

Sample Questions

Question 1: How caesium and potassium can be used for commercial purposes?

Answer: 

Caesium and Potassium have a special ability to lose electrons by absorbing energy from sunlight when light rays fall on these elements and this results in a photoelectric effect due to which caesium and potassium are used commercially as electrodes in photoelectric cells.

Question 2: Give 3 medical uses of Magnesium.

Answer: 

  • Magnesium is used in medicines to take antacids. 
  • Magnesium oxide is used in the treatment of constipation.
  • Magnesium is also used as anaesthesia when salts of magnesium are injected into the human body.

Question 3: Why Lithium has different properties from the rest of its group members?

Answer: 

There are mainly two reasons for the different properties of lithium from its group members: 

  1. Size: Atomic size of lithium is really very small
  2. Polarising power: Polarising power can be defined as the ratio of the charge of an element to the radius of that element. Lithium has high polarising power as its size is very small so the charge divided by radius gives a big number.

Question 4: Why Beryllium has different properties from the rest of its group members?

Answer: 

There are mainly two reasons for the different properties of beryllium from its group members:

  1. Size: Atomic size of beryllium is really very small as compared to other elements of the same group so it does not follow the same trends as other alkaline earth metals do.
  2. Atomic Number: As the atomic number of beryllium is 4 so its coordination number cannot be greater than 4 while other members of the same group can have a coordination number 6 also.

Question 5: Why radium do not have much biological importance?

Answer: 

Radium is radioactive in nature and due to its toxicity, there is no biological use of Radium. In the medical field, it is only used to produce radon gas which is used in the treatment of cancer. 


My Personal Notes arrow_drop_up
Recommended Articles
Page :

Start Your Coding Journey Now!