Calculate the disintegration energy: Use Einstein’s mass-energy equivalence formula, E mc2 E 3 1029 (3 108)2 2.7 1012 J
Convert disintegration energy from joules to electronvolts:
E 2.7 1012 1.6 1019 1.7 107 eV 17 MeV
EXERCISE 23.1 MASS–ENERGY CONVERSIONS
Refer to the Periodic table on p. 495 when answering these questions. Take the speed of light as 2.998 108 m s1 in all these questions.
Q1 Polonium-210 is an alpha-emitter, decaying into lead-206 in accordance with the following
equation: 84
210Po : 82 206Pb 2 4He Q
where Q is the disintegration energy.
Calculate: (i) the disintegration energy Q (ii) the kinetic energies of both the lead-206 and the alpha particle.
Mass of 84 210Po 3.48571025 kg;mass of 82 3.41821025 kg;mass of 6.645 1027 kg.
2 4He
Q2 Calculate the energy of a proton when it is accel- erated through a potential difference of 700 kV. (Charge on an electron 1.6022 1019 C.)
206Pb ,
Q3 Cockcroft and Walton carried out the first transmutation by an artificially accelerated particle when they bombarded lithium with high-energy protons in 1932. By the end of that decade, many similar experiments had been carried out. One such experiment involves bombarding fluorine with oxygen with the emission of an alpha particle.The equation for
this reaction is
1 1H 9 19F : 8 16O 2 4He
.
Calculate the energy released, giving your answer in electronvolts.
(Mass of proton 1.008 u; mass of fluorine nucleus 19.998 u; mass of oxygen nucleus 15.995 u; mass of -particle 4.003 u; 1 u 1.66 1027 kg; charge on an electron 1.6022 1019 C.)
Antimatter ANTIMATTER
Antimatter is matter composed of antiparticles; antiparticles are subatomic particles of matter that are identical to another subatomic particle in mass but opposite to it in electric charge.
Each particle has its own antiparticle.
Positron The first antiparticle to be observed was the antiparticle of the electron. It was named the positron, e. It has the same mass as an electron, e, with the same size charge, the difference being the charge on a positron is positive.
