Exam Q 18

Question 1

Who discovered the existence of isotopes using the mass spectrometer?

Answer 1

Francis Aston

Question 2

What are isotopes? define

Answer 2

Isotopes are atoms of the same element (same atomic number) which have different mass numbers due to the different number of neutrons in the nucleus

Question 3

What is the principle of the mass spectrometer? define

Answer 3

It is that charged particles moving in a magnetic field are deflected to different extents according to their masses and are thus separated according to these masses

Question 4

How do you calculate the relative atomic mass of neon-20 at 90.50% and neon-22 at 9.5%

Answer 4

In 100 atoms of neon there are:

90. 5 of these are of mass 20 = 90.5 x 20 = 1,810
91. 5 are of mass 22 = 9.5 x 22 =

1,810 + 209 = 2,019 (total mass of 100 electrons)

divide by 100 = 20.19 average mass of 1 atom = relative atomic mass of neon