The s-Block Elements

  • Question 149
    CBSEENCH11007127

    Explain the significance of sodium, potassium, calcium and magnesium in biological fluids ?

    Solution

    The significance of sodium and potassium in biological fluids: K+ and Na+ cations are present in the red blood cells. The ratio of K+ to Na+ ions in a mammal such as human beings, rabbit, rats and horses is 7:1. These cations accumulate in cells and create a concentration gradient and potential in the membrane. Electric pulse in the every is generated when a chemical is released during activation of discharge the membrane potential.

    Magnesium is part of chlorophyll the green colouring matter of plants. Photosynthesis takes place only in the presence of chlorophyll.

    Calcium is present in the form of calcium phosphate Ca3(PO4)2 in bones, Ca and Mg play a key role in the formation of phosphorus- oxygen linkage in biological systems for storage of energy. The pyrophosphate hydrolysis which releases energy is controlled by calcium ions. These ions perform important biological functions such as maintenance of ion balance and nerve impulse conduction. 

    Question 150
    CBSEENCH11007128

    State as to why sodium is found to be more useful than potassium.

    Solution

    Sodium ions which are present in blood plasma and in the interstitial fluid help:
    (i) in the transmission of nerve signals.
    (ii) in regulating the flow of water across cell membrane.
    (iii) in the transport of sugars and amino acids. Thus sodium is found to be more useful than potassium (K+ ions are present in the cell fluids).

    Industrial uses of sodium metal reflect its strong reducing power, about 60% of world production of sodium are used to male tetraethyl lead PbEt4 for the gasoline antiknocks.

    i) It is also used in dye industry.

    ii) It is also used for detecting the presence of nitrogen, Sulphur and halogen in organic compounds. It is widely used as sodium amalgam as a reductant.

    Question 151
    CBSEENCH11007129

    Name the elements of group 2. Write down their electronic configurations ?

    Solution

    The metallic elements beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra) constitute group 2 of the periodic table. Radium is a radioactive element. These are known as alkaline earth metals. 
    Electronic configuration. The atoms of alkaline earth metals have two electrons in s-orbital outside a noble gas core. Therefore, their general electronic configuration is [Noble gas] ns2 where n = 2 to 7.
    The electronic configuration of alkaline earth metals are given below:

    Element At. No.  Electronic configuration
    Beryllium (Be) 4 [He] s2
    Magnesium (Mg) 12 [Ne] 3s2
    Calcium (Ca) 20 [Ar] 4s2
    Strontium (Sr) 38 [Kr] 5s2
    Barium (Ba) 56 [Xe] 6s2
    Radium(Ra) 88 [Rn] 7s2
    Question 152
    CBSEENCH11007130

    Why elements of group 2 are called alkaline earth metals?

    Solution

    The oxides of these elements of Group 2 were known much earlier than the metals themselves. These oxides were alkaline in nature and were found in the earth's surface. Thus, the elements of group 2 were given the name alkaline earth metals.

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