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Chapter 4 Structure of the Atom

Until the structure of atom reveals it was thought atom are indivisible but as the modern technology is advancing more and more. We came to know that these atoms are made of subparticle and they together form an atom. An atom contain positive and negative charges, but yet is electrically stable.

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Exercise 1

Exercise 2

Exercise 3

Exercise 4

  • Q1

    Write the distribution of electrons in carbon and sodium atoms.

    Ans:

    The distribution of electrons in Carbon and Sodium atom :
    Carbon :          Atomic no. of Carbon = 6
                             no. of protons = 6
                         no. of protons = no. of electrons
                         Distritribution of electron = K L
                                                                    2  4
    Sodium : 
            Atomic no. of Sodium = 11
                              no. of protons = 11
                           no. of protons = no. of electrons
                          Distritribution of electron = K L M
                                                                     2 8 1


    Q2

    If K and L shells of an atom are full, then what would be the total number of electrons in the atom?

    Ans:

    K shell can hold 2 electrons and L shell can hold 8 electrons.When both the shells are full, there will be (8 + 2) 10 electrons in the atom.


Exercise 5

  • Q1

    How will you find the valency of chlorine, sulphur and magnesium?

    Ans:

    Valency of a particle is the quantity of electrons acquired, lost or shared to finish the octet of electrons in the valence shell.
    Valency of chloride: It has electronic design = 2, 8, 7
    In this manner, one electron is acquired to finish its octet thus its valency is 1.
    Valency of sulfur: Its has electronic design = 2, 8, 6
    In this manner, 2 electrons are acquired to finish its octet and henceforth its valency = 2
    Valency of magnesium : It has electronic design = 2, 8, 2
    Accordingly, it can lose two electrons to achieve octet and thus its valency = 2


Exercise 6

Exercise 7

  • Q1

    For the symbol H,D and T tabulate three sub-atomic particles found in each of them.

    Ans:

    H, D, and T are the three isotopes of hydrogen with similar nuclear number and distinctive mass quantities of 1, 2 and 3 separately.
     

    Element Symbol Number of Electrons Number of Protons Number of Neutrons
    Hydrogen H 1 1 0
    Deuterium D 1 1 1
    Tritium T 1 1 2

    Q2

    Write the electronic configuration of any one pair of isotopes and isobars.

    Ans:

    (a) Isotopes: Isotopes are iotas which have similar number of protons however extraordinary number of neutrons. They have same nuclear number yet unique mass number.
    Model: Carbon particle exists as 6C12 and 6C14 however when their electronic configuration is K-2; L-4
    (b) Isobars: Isobars are particles which have a similar mass number however extraordinary nuclear number.
    Model: Electronic configuration of 20Ca40is – K-2; L-8; M-8; N-2 and of 18Ar40 is – K-2; L-8; M-8


Exercise 8

Popular Questions of Class 9 Science