Question

24. The composition of two atoms P and Q is given below :
Atom
Neutrons
Protons
Electrons
P
13
11
Q
12
11
11
(a) What is the mass number of P?
(b) What is the mass number of Q?
(c) How are P and Q related to each other?
(d) Which element do these atoms represent?
(e) Are the elements metals or non-metals?
26. The table below shows the elements from P to T, such that a pair of elements is an isotope. Identify the pair​

Answer 1

Answer:

Explanation:Atomic mass is based on a relative scale and the mass of 12C

(carbon twelve) is defined as 12 amu; so, this is an exact number.

Why do we specify 12C? We do not simply state that the mass of a C atom is

12 AMU because elements exist as a variety of isotopes.

Carbon exists as two major isotopes, 12C, and 13C ( 14C exists and has

a half life of 5730 y, 10C and 11C also exist and their half lives are

19.45 min and 20.3 days respectively). Each carbon atom has the

same number of protons and electrons, 6. 12C has 6 neutrons, 13C has

7 neutrons, and 14C has 8 neutrons and so on. So, we must specify

which C atom defines the scale.

All the masses of the elements are determined relative to