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Question
Explain the following :
(a) Electrovalent compounds conduct electricity in molten or aqueous state.
(b) Electrovalent compounds have a high melting point and boiling point while covalent compounds have low melting and boiling points.
(c) Mass of an atom is concentrated inside the nucleus of an atom.
(d) Atoms combine by transfer and sharing of electrons (s).
(e) An element has atoms with different mass number.
Explain the following :
(a) Electrovalent compounds conduct electricity in molten or aqueous state.
(b) Electrovalent compounds have a high melting point and boiling point while covalent compounds have low melting and boiling points.
(c) Mass of an atom is concentrated inside the nucleus of an atom.
(d) Atoms combine by transfer and sharing of electrons (s).
(e) An element has atoms with different mass number.
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Solution
(a) Electrovalent compounds in the solid state do not conduct electricity because movement of ions in the solid state is not possible due to their rigid structure. But these compounds conduct electricity in the molten state. This is possible in the molten state since the electrostatic forces of attraction between the oppositely charged ions become weak. Thus, the ions move freely and conduct electricity.
(b) The atoms of covalent compounds are bound tightly to each other in stable molecules, but the molecules are generally not very strongly attracted to other molecules in the compound. On the other hand, the atoms (ions) in electrovalent compounds show strong attractions to other ions in their vicinity. This generally leads to low melting points for covalent solids, and high melting points for electrovalent solids.
c)An atom has a nucleus with electrons outside it. The atom is made from a central nucleus with electrons around the outside. The electrons have a negative charge and very little mass. Most of the mass of the atom is concentrated in the nucleus, which has a positive charge.
d)Covalent bond is the bond formed in which two atomsshare a pair of electrons and form molecules. The bondthat results whenever unequal sharing occurs is called polar covalent bond while equal sharing of electrons iscalled non polar covalent bond
e)Elements are known to have isotopes - with same no. of protons but different no. of neutrons. Therefore the atomic number is the same but the atomic mass is different.Hydrogen is a single element but it has 3 isotopes, each having different mass number.
(b) The atoms of covalent compounds are bound tightly to each other in stable molecules, but the molecules are generally not very strongly attracted to other molecules in the compound. On the other hand, the atoms (ions) in electrovalent compounds show strong attractions to other ions in their vicinity. This generally leads to low melting points for covalent solids, and high melting points for electrovalent solids.
c)An atom has a nucleus with electrons outside it. The atom is made from a central nucleus with electrons around the outside. The electrons have a negative charge and very little mass. Most of the mass of the atom is concentrated in the nucleus, which has a positive charge.
d)Covalent bond is the bond formed in which two atomsshare a pair of electrons and form molecules. The bondthat results whenever unequal sharing occurs is called polar covalent bond while equal sharing of electrons iscalled non polar covalent bond
e)Elements are known to have isotopes - with same no. of protons but different no. of neutrons. Therefore the atomic number is the same but the atomic mass is different.Hydrogen is a single element but it has 3 isotopes, each having different mass number.
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