Few physics questions: 1) An atom will emit photons when one of its electrons go

Question

Few physics questions:

1) An atom will emit photons when one of its electrons goes from

Select one:

A. the K shell to the M shell.

B. the K shell to the N shell.

C. the M shell to the N shell.

D. the N shell to the L shell.

E. the K shell to the L shell.

2) Which one of the following quantities is not necessarily conserved in nuclear reactions?

Select one:

A. linear momentum

B. angular momentum

C. electric charge

D. number of protons

E. number of protons and neutrons

3) How many neutrons are there in the nucleus Gold?

B. 79

C. 24

D. 134

E. 55

(note: answer is NOT 120).

Explanation / Answer

1.D

2.B

3.Gold, (symbol Au) has an atomic number of 79 i.e. each gold atom has 79 protons in its nucleus. The atomic mass of the gold atom is 196.967 and the atomic radius is 0.1442nm. Interestingly this is smaller than would be predicted by theory. The arrangement of outer electrons around the gold nucleus is based on 14 4f shell electrons, 10 5d shell electrons and a single 6s shell electron.

Whilst the number of protons in a gold nucleus is fixed at 79, the number of neutrons can vary from one atom to another giving a number of isotopes of gold. However, there is only one stable non-radioactive isotope accounting for all naturally found gold

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