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The Fundamental Unit of Life
What are X-rays?
X-rays are electro-magnetic waves with very short wavelengths. These are formed when fast moving electrons are suddenly stopped by putting some obstructions like a block of tungsten metal. For example, in the discharge tube, X-rays can be produced if the electrons/ cathode rays are made to strike against the metal target.
The important feature of X rays is that it can penetrate or pass through the human body and produce shadow-like images of structures such as bones, some of the organs, and signs of disease and injury.
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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
Number of valence electrons in Cl- ion are
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