Question

Numericals :-

(a) While measuring the length of a knitting needle the reading of the scale at

one end is 3 cm and at the other end is 33.1 cm. What is the actual length of

the needle ?

(b) Mohan needs 7 metre of cloth to stitch a dress where as Sohan needs

825cm. Who needs more cloth for stitching the dress and by how much ?​

Answer 1

Explanation:

We know that : <br> Mass number = Atomic number + No. of neutrons <br> So, 23 = Atomic number + 12 <br> And, Atomic number = 23 - 12 <br> = 11 <br> The element having atomic number 11 is sodium and its symbol is Na. If, however, we indicate the atomic number and mass number also, then the symbol becomes

, where 11 is the atomic number and 23 is the mass number.