TED Ed – 4 min

23892 U

→ 23490 Th

+ 42 He

+

ɣ

Write a nuclear reaction for…

Uranium-238 decays into Thorium-234:

92 = 90 + 2 (conservation of atomic number)

238 = 234 + 4 (conservation of atomic mass)

Uranium nucleus emits 2 protons and 2 neutrons:

- an alpha particle (=helium nucleus)

Don’t forget the gamma radiation!

13153 I

→ 13154 Xe

+ 0-1 e

+

ɣ

Write a nuclear reaction for…

Iodine-131 decays into Xenon-131:

53 = 54 – 1 (conservation of atomic number) 131 = 131 + 0 (conservation of atomic mass)

Physically, what is going on here?

*** a neutron changes into a proton (plus electron) ***

Don’t forget the gamma radiation!

147 N

→ 178 O

+ 42 He

+

Try this: splitting the atomRutherford fired alpha particles into a jar of nitrogen gas. He discovered the products were oxygen-17 + another particle. Write the nuclear equation for the reaction:

7 + 2 = 8 + 1 (conservation of atomic number) 14 + 4 = 17 + 1 (conservation of atomic mass)

11 H

So what actually is the other particle produced?

- a hydrogen nuclei (a proton!)

- no gamma (because not a decay)

Today’s Learning:

1) Balance equations for nuclear reactions

2) Use E=mc2 to calculate the energy released in a nuclear reaction

or:

2E mc

2/m E c

In Rutherford’s experiment: (printed this for you!)

147 N

→ 178 O

+ 42 He

+ 11 H

The rest masses of the particles involved are:

1) Calculate the total mass before and after the reaction

The alpha particle had an initial kinetic energy of

12.50 x 10-13 J. After the reaction, the kinetic energy ofthe oxygen atom was 6.4 x 10-14J and the proton was 9.48 x 10-13J.

3) Verify Einstein’s theory of mass-energy equivalence

2) Calculate the total energy before and after the reaction

Check you understand and can do this yourself:Read pages 191-194

Complete and mark Activity 12A, Q1,2,3

Due…

Symphony of ScienceThe Quantum World - 3min 29sec