How will you find the valency of chlorine, sulphur and magnesium?
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
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With the help of Table 4.1, find out the mass number of oxygen and sulphur atom.
For the symbol H,D and T tabulate three sub-atomic particles found in each of them.
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Define valency by taking examples of silicon and oxygen.
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Draw a sketch of Bohr’s model of an atom with three shells.
Describe Bohr’s model of the atom.
Write the electronic configuration of any one pair of isotopes and isobars.
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State the universal law of gravitation.
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Chair, air, love, smell, hate, almonds, thought, cold, cold-drink, smell of perfume.
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What is meant by a pure substance?
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In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium observations are in agreement with the law of conservation of mass.
sodium carbonate + ethanoic acid → sodium ethanoate + carbon dioxide + water
State any two conditions essential for good health.
How is our atmosphere different from the atmospheres on Venus and Mars?
Who discovered cells, and how?
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In what direction does the buoyant force on an object immersed in a liquid act?
Calculate the molecular masses of H2, O2, Cl2, CO2, CH4, C2H6, C2H4, NH3, CH3OH.
Which of the following has more inertia: (a) a rubber ball and a stone of the same size? (b) a bicycle and a train? (c) a five-rupees coin and a one-rupee coin?
Which organelle is known as the powerhouse of the cell? Why?
What are macro-nutrients and why are they called macro-nutrients?
Distinguish between speed and velocity.
Why are sound waves called mechanical waves?
Identify the type of tissue in the following: skin, bark of tree, bone, lining of kidney tubule, vascular bundle.
What are the methods of preventing or reducing soil erosion?