The atomic number of calcium and argon are 20 and 18 respectively, but
the mass number of both these elements is 40. What is the name given to
such a pair of elements?
Match the names of the Scientists given in column A with their contributions
towards the understanding of the atomic structure as given in column B
(A) (B)
(a) Ernest Rutherford (i) Indivisibility of atoms
(b) J.J.Thomson (ii) Stationary orbits
(c) Dalton (iii) Concept of nucleus
(d) Neils Bohr (iv) Discovery of electrons
(e) James Chadwick (v) Atomic number
(f) E. Goldstein (vi) Neutron
(g) Mosley (vii) Canal rays
In response to a question, a student stated that in an atom, the number of
protons is greater than the number of neutrons, which in turn is greater
than the number of electrons. Do you agree with the statement? Justify
your answer.
In the atom of an element X, 6 electrons are present in the outermost shell.
If it acquires noble gas configuration by accepting requisite number of
electrons, then what would be the charge on the ion so formed?
Write down the electron distribution of chlorine atom. How many electrons
are there in the L shell? (Atomic number of chlorine is 17).
One electron is present in the outer most shell of the atom of an element X.
What would be the nature and value of charge on the ion formed if this
electron is removed from the outer most shell?
Is it possible for the atom of an element to have one electron, one proton
and no neutron. If so, name the element.
Atomic models have been improved over the years. Arrange the following
atomic models in the order of their chronological order
(i) Rutherford’s atomic model
(ii) Thomson’s atomic model
(iii) Bohr’s atomic model
(a) (i), (ii) and (iii)
(b) (ii), (iii) and (i)
(c) (ii), (i) and (iii)
(d) (iii), (ii) and (i)
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