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The Fundamental Unit of Life
Give the properties and use of X-rays.
Properties of X-rays:
(i) X-rays travel in straight lines with speed of light.
(ii) X-rays are not deflected by electrical and magnetic fields.
(iii) They are more penetrating than cathode rays.
(iv) They can pass through opaque materials such as black paper and affect a photographic plate wrapped in it.
(v) They cause fluorescence in several materials. A plate coated with barium platinocyanide, zinc sulphide etc. becomes luminous when exposed to X-rays.
Uses of X-rays :
(i) They are useful to locate the broken parts of the body such as bones because solid bone stops X-rays from passing through it and are seen as an opaque image in the X-rays film.
(ii) They are used by detective departments to examine the contents of a parcel without opening it and to detect diamonds/gems concealed by smugglers within their body.
(iii) They are used in the treatment of tumours and cancer in the animals and the human beings.
(iv) They are quite helpful in the study of the nature and structure of the materials.
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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
Number of valence electrons in Cl- ion are
Which one of the following is a correct ? Electronic configuration of sodium
(a) 2, 8,2 (b) 8, 2, 1 (c) 2, 1, 8 (d) 2, 8, 1.
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