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The Fundamental Unit of Life
What is meant by atomic no. of an element ? Does the atomic number of an element change when its atoms form ions ? Give one example each of diatomic and triatomic molecules.
Atomic number can be defined as the number of protons present in the nucleus of an atom. Atomic number of an element does not change when it forms ions because the number of protons does not alter. For example diatomic molecule—oxygen (O2) triatomic molecule- water (H2O), O3 (ozone), the atomic number of oxygen is 8 in all case.
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Summarize the rules for writing of distribution of electrons in various shells for the first eighteen elements.
Define valency by taking examples of silicon and oxygen.
Explain with examples, (i) Atomic number, (ii) Mass number, (iii) Isotopes, and (iv) Isobars. Give any two uses of isotopes also.
Na+ has completely filled K and L-shells. Explain.
If Z = 3, what would be the valency of the element? Also, name the element.
Composition of the nuclei of two atomic species X and Y are given as under
X Y
Protons = 6 6
Neutrons= 6 6
Give the mass numbers of X and Y. What is the relation between the two species?
For the following statements, write T for True and F for False.
(a) J.J. Thomson proposed that the nucleus of an atom contains only nucleons.
(b) A neutron is formed by an electron and a proton combining together. Therefore, it is neutral.
(c) The mass of an electron is about 1/2000 times that of proton.
(d) An isotope of iodine is used for making tincture iodine, which is used as a medicine.
Rutherford’s α-particle scattering experiment was responsible for the discovery of
Isotope of an element has
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