Q9 of 59 Page 1

An element 'X' belongs to 3rd period and group 13 of the Modern Periodic Table.

(a) Determine the valence electrons and the valency of 'X'.


(b) Molecular formula of the compound formed when 'X' reacts with an element 'Y' (atomic number = 8).


(c) Write the name and formula of the compound formed when 'X' combines with chlorine.

(a)Since it belongs to group 13, therefore no. of valence electrons= 3


The Valency of element X is 3


(b)When 'X' reacts with element 'Y', the compound formed will be:



Therefore, the Molecular formula of compound formed is X2Y3.


(c)When X combines with chlorine:


Atomic no of X = 13


i.e. X is Aluminum Al


Valency of X is 3


Valency of chlorine is 1


Therefore, the molecular formula will be:



Compound: AlCl3


More from this chapter

All 59 →
7

The position of eight elements in the Modem Periodic Table is given below where atomic numbers of elements are given in the parenthesis.


(i) Write the electronic configuration of Ca.


(ii) Predict the number of valence electrons in Rb.


(iii) What is the number of shells in Sr?


(iv) Predict whether K is a metal or a non-metal.


(v) Which one of these elements has the largest atom in size?


(vi) Arrange Be, Ca, Mg and Rb in the increasing order of the size of their respective atoms.

 8

Write three different chemical reactions showing the conversion of ethanoic acid to sodium ethanoate. Write balanced chemical equation in each case. Write the name of the reactants and the products other than ethanoic acid and sodium ethanoate in each case.

 17

The image formed by a spherical mirror is real, inverted and is magnification -2. If the image is at a distance of 30 cm from the mirror, where is the object placed? Find the focal length of the mirror. List two characteristics of the image formed if the object is moved 10 cm towards the mirror.

 24

(a) Define focal length of a divergent lens.

(b) A divergent lens of focal length 30 cm forms the image of an object of size 6 cm on the same side as the object at a distance of 15 cm from its optical center. Use lens formula to determine the distance of the object from the lens and the size of the image formed.


(c) Draw a ray diagram to show the formation of image in the above situation.