Long Answer TypeA, B, C are three elements, B is an inert gas element other than helium; with this information, complete the table given below:
| Element | Atomic No. | No. of electrons in the valence shell | Group to which element belongs |
| A | Z - 1 | ||
| B | Z | ||
| C | Z+1 |
Also, explain the following:
(i) Electron gain enthalpy of element A has large negative value than that of C.
(ii) Ionisation enthalpy of element C is less than that of A.
(iii) Electron gain enthalpy of B is positive.
Define electronegativity. Explain the factors influencing electronegativity. How does it vary along periods and groups? what are its units?
Short Answer TypeExplain giving various reasons for the variation of electronegativity along a period and along a group.
Long Answer TypeWhat is the basic difference between the terms electronegativity and electron gain enthalpy?
Short Answer TypeHow would you react to the statement that the electronegativity of N on Pauling scale is 3.0 in all the nitrogen compounds?
Long Answer TypeGive a brief account of valence ?
Valence. The electrons present in the outermost shell (or valence shell) of the elements are called valence electrons and they normally represent the valency of the element.
In the case of representative elements (s-and p-block elements), valency is either equal to the number of valence electrons or eight minus the number of valence electrons. For example
In HCl, the valency of H =1
In CaCI2. the valency of Ca = 2 (valence electrons = 2)
In NH3, the valency of N = 3 {8-5} (valence electrons = 5)
Variation along a period: The number of electrons in the valence shell increases from one to eight as we move from left to right in the periodic table. The valency with respect to hydrogen initially increases from 1 to 4 and then decreases from 4 to 0.
LiH BeH2 BH3 CH4 NH3 H2O HF Ne
1 2 3 4 3 2 1 0
In a similar manner, the valency with respect to chlorine also initially increases from 1 to 4 and then decreases from 4 to 0.
Variation in a group: The valency of the element depends on upon its valence shell configuration. Since in a group, the valence shell configuration of the elements remains almost the same, they exhibit a common valency. For example, all the elements of group 1 have valency one and those of group 2 have valency two.
The valence of representative elements is either equal to the number of valence electrons or eight minus the number. What is the basis of their rule?
Short Answer TypePredict the formulae of the stable binary compounds that would be formed by the following pairs of elements:
silicon and oxygen
Predict the formulae of the stable binary compounds that would be formed by the following pairs of elements:
aluminium and bromine
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