Name: Periods in the Modern Periodic Table
Uploaded: 2019-07-19
Duration: 5 min 31 s
Description: The general characteristics of periods are identified by its total number of shells in an atom or period number. The electronic configuration of an element d...

Question

Two elements X and Y belong to groups I and 2 respectively in the same period. Compare them with respect to (a) the number of electrons in the outermost shell, (b) the number of valence electrons, (c) metallic character, (d) size of the atoms and (e) formula of the oxides, hydrides and chlorides.

Accepted Answer

(a)

X Y

The element that belongs to group 1 is an alkali metal with the general outer electronic configuration of ${ns}^{1}$ The element Y belongs to group 2 is an alkaline earth metal with the general outer electronic configuration of ${ns}^{2}$

(b)

X Y

In order to obtain the noble gas electronic configuration, they lose one and only valence electron. In order to obtain the noble gas electronic configuration, they lose 2 valence electrons.

(c)

X Y

A more electropositive element has a more metallic character. X is more metallic than Y. Across the period metallic character decreases, thus Y is less metallic than X.

(d)

X Y

Alkali metals are at the extreme left side of the periodic table and across the period the size of elements decreases. Thus the size of X is more than that of Y. Across the period the size of elements decreases, thus the size of Y is less than that of X.

(e) Formula of oxides

X Y

Formula of oxides of X is $X_{2} O$ , for example, ${Na}_{2} O$ . Formula of oxides of Y is $YO$ , for example, $MgO$ .

Formula of hydrides:

X Y

Formula of hydrides of X is $XH$ , for example, $NaH$ . Formula of hydrides of Y is ${YH}_{2}$ , for example, ${MgH}_{2}$

Formula of chlorides:

X Y

Formula of chlorides of X is $XCl$ , for example, $NaCl$ . Formula of chlorides of Y is ${YCl}_{2}$ , for example, ${MgCl}_{2}$ .

Two elements X and Y belong to groups I and 2 respectively in the same period. Compare them with respect to (a) the number of electrons in the outermost shell, (b) the number of valence electrons, (c) metallic character, (d) size of the atoms and (e) formula of the oxides, hydrides and chlorides.

Important Questions on Periodic Classification of Elements

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