Question

give a reason for each of the following ​

Answer 1

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1)-» Isotopes of an element have different physical properties because they have different mass numbers. When it comes to physical properties of isotopes including mass, melting or boiling point, density, and freezing point, they are all different. The physical properties of any isotope are largely determined by its mass.

2)-» Water is a compound because it is made up of water molecules. There is no such thing as water atoms. Water molecules are made of hydrogen and oxygen atoms, in the definite proportion of two hydrogens for one oxygen

3)-» The symbols for the elements are derived from their Latin and Greek synonyms to avoid confusion due to English words. For Sodium the symbol is Na derived from Natrium, because the symbol S was already taken for Sulphur so Si is the symbol for Silicon

4)-» Hardness in laundry water is a problem because the minerals that cause hardness interfere with the cleaning action of soaps and detergents. As a result, larger amounts of soaps and detergents are needed to counteract the minerals, and laundry results are not as good as when there is no hardness present.

5)-» Some elements show variable valency because of the different electronic configurations. An atom of an element can sometimes lose more electrons than are present in its valence shell i.e. loss from the penultimate shell and hence exhibit more than 1 or variable valency

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Answer 2

Answer:

1.This is because isotopes of an element have the same number of electrons as an atom of that element. But they have different number of neutrons which affects the mass number. Mass number determines the physical properties. Hence isotopes have similar chemical properties but different physical properties

2.Water is considered as compound because: (i) Water is composed of two elements:hydrogen and oxygen. (ii) The ratio of hydrogen and oxygen by mass in any sample of pure water is the same. ... (iv) Water can be decomposed by chemical means (e.g., electrolytically) into hydrogen and oxygen.

3.The symbols for the elements are derived from their Latin and Greek synonyms to avoid confusion due to English words. For Sodium the symbol is Na derived from Natrium, because the symbol S was already taken for Sulphur so Si is the symbol for Silicon

4.Hard water contains the calcium and the magnesium ions in them. This scum wastes a lot of soap to form the micelle to clean the clothes. ... Thus the soaps are not used to wash clothes with hard water.

5.(i) Certain elements have more than one valency. They exhibit variable valency. For example, copper, tin, iron and mercury exhibit variable valency. Copper combines with oxygen to form cuprous oxide (Cu2O) and cupric oxide (CuO).

(ii)Some elements show variable valency because of the different electronic configurations. An atom of an element can sometimes lose more electrons than are present in its valence shell i.e. loss from the penultimate shell and hence exhibit more than 1 or variable valency.

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