Try This
Complete "Practice Problems" 1 to 3 on page 800 of your physics textbook.


Antineutrinos

In beta-negative decay, a neutron converts into a proton, electron, and antineutrino.  The proton is retained by the nucleus, keeping the atomic mass constant while increasing the atomic number and, thus, changing the type of element. The emitted electron is called a beta particle to distinguish it from the electrons around the nucleus.  According to the conservation laws, beta decay can be represented by the following equation.

Symbol

Symbol

SI Unit

X - parent element

X

--

Y - daughter element

Y

--

β - beta particle

β

- antineutrino

--












The antineutrino is not shown in the Nuclear Decay Gizmo.



antineutrino: ν, a tiny subatomic particle with no charge emitted with e-10 in beta decay.



neutrino: ν, a tiny subatomic particle with no charge emitted with a positron in beta-positive decay

Read
Read about the neutrino on page 804 of the textbook.

Self-Check

SC 3. The following questions relate to the beta decay of plutonium-241.

a. What is the beta decay equation?

b. What is the parent element and what are the daughter elements?

c. How does this decay equation obey the law of conservation of charge?

d. How does this decay equation obey the law of conservation of nucleons?

 


Contact your teacher if your answers vary significantly from the answers provided here.

SC 3.


  1. See above

  2. The parent element is plutonium-241 and the daughter element is americium-241. (Electrons and antineutrinos are not elements.)

  3. The decay equation obeys the law of conservation of charge because there are 94 protons before the transmutation and after there are 95 protons in the americium but negative one on the electron [95+ (−1) = 94].  [A neutron (q = 0) changes into a proton (q = 1) and an electron (q = −1).]
  4. The decay equation obeys the law of conservation of nucleons because there are 241 nucleons before the transmutation and 241 nucleons after the transmutation.  (The beta particle and the antineutrino are ejected from the americium 241 atom.)


Try This
Complete "Practice Problem" 1.(a) associated with Example 16.8 and "Practice Problem" 1.(a) associated with Example 16.9 on page 803. Remember that each reaction also produces a beta particle and an antineutrino.


Read
Read about antimatter and the positron on pages 804 and 805.  Note, in Example 16.10 the extra electron that must be taken into account in the mass defect.


Self-Check

Answer the following self-check question then click the "Check your work" bar to assess your response.
SC 4. How does the weak nuclear force relate to beta decay (both positive and negative decay)?


antimatter: a form of matter that has properties opposite to its normal-matter counterpart



positron: the antimatter to an electron

(It is the same type of particle but has an opposite charge.  Unlike electrons and positrons, positirons are scarce.)


Contact your teacher if your answer varies significantly from the answer provided here.

SC 4. The weak nuclear force is involved in the transformation of a neutron into a proton and electron in beta-negative decay. In beta-positive decay, it would be involved in the transformation of a proton into a neutron and a positron.