Correct Answer: (3) 3.82 days and alpha decay

Why:

Radon is the chemical element Rn with an atomic number of 86 and atomic mass of 222.  Radon is a colorless, odorless, tasteless, naturally occurring radioactive noble gas.  It is formed from the decay of radium, and is considered a health hazard. Rn222 is the most stable isotope of Radon and has a half life of 3.8 days.

Alpha decay is the emission of a ⁴₂He.   The atomic number and mass numbers of the new "daughter" nuclide and the He product will add to equal the numbers of the "parent" nuclide.    Beta decay is either the emission of an electron (_-1⁰e), the capture of an electron(_-1⁰e) or the emission of a positron (₊₁⁰e).  Again the atomic numbers mass numbers must add up.  In the case of an emission the Parent nuclide's numbers equal the sum of the electron's and the daughter nuclide.  In the case of a capture the daughter nuclide's number add to the sum of the electron and the parent nuclide.  Notice that the atomic mass (top number) of the electron is 0 and so the atomic mass of the nuclide should not change in beta decay.

Answering this question:

The best way to answer this question is to be familiar with Radon.  If you don't know the half life of Rn222 but you know that it is the most stable isotope it would make sense to choose the longest answer.  If you know that Rn222 is a product of Radium it is also possible to know if it was alpha decay or beta decay.  Radium has the atomic number 88 and atomic mass 226.  Because both numbers change it must be alpha decay.  Therefore the best answer is (3)

Correct Answer: (2)

Why:

Transmutation is the change of one element into another element.  The only way to accomplish this is to make a change in the nucleus of an atom, because simply changing the atomic mass is to make a new isotope of the same element.  To change an element into another element the nucleus (atomic number) must change, and it must be done with a nuclear reaction.

Considering all your possible answers lets look at (1) first.  In this equation a gamma ray is produced, however the element, atomic mass, and atomic number have all remained the same.  This can not qualify as a transmutation.  In (3) there is a change in the compounds as a result of the chemical reaction however the elements themselves, and their nucleus have remained unchanged.  Answer (4) is depicting the use of a catalyst in a reaction.  However, we remember that a catalyst is unchanged in a chemical reaction and only serves the purpose of speeding up the reaction.  This leaves answer (2).  Upon a closer look, it can be seen in this equation the carbon element is changed into a Nitrogen atom.  The carbon's nucleus emits an electron and changes the atomic number from 6 to 7 turning it into a Nitrogen.

Answering this question:

The key to answering this question is to know what transmutation means.  It is best to know its chemical definition as discussed above.  But, if you are drawing a blank, looks at the word logically.  A mutation is a change.  This helps you eliminate (1) and (4) because there are no changes occurring in those equations.   When weighing (2) and (3), consider which has the biggest change.  While (3) has compounds reacting and making new products (2) is a fundamental change and looks more like a true mutation.  Viola you've found the correct answer.

Correct Answer: (4)

Why:

Positron decay is a type of beta decay and is characterized by a proton of the nucleus being converted into a neutron, a positron, and a neutrino.  A positron is the antimatter equivalent of an electron.  It has the same mass as an electron but the opposite charge. (4) is the only answer emitting a positive electron and therefore must be the correct answer.

Answering this question:

The only way to solve this question with any certainty is to know that a positron is a positive electron.  With that knowledge the question because a rather simple and straightforward problem.

Correct Answer (3)

Why:

Fusion is a reaction in which two atoms of hydrogen combine together or fuse to form a Helium atom.  In this process some of the mass of the hydrogen is converted into energy.  The easiest fusion reaction is that which is displayed in answer (3).  By combining deuterium, ²₁H (heavy hydrogen) with tritium ³₁H (heavy heavy hydrogen) to obtain a Helium atom and one neutron.

Answering this question:

If you know what fusion is the best answer is obvious.  If you are unsure it may be possible to eliminate a few of the answers to increase your chances in a correct answer.  Choice (1) is obviously water changing from gas to liquid.  We know that nothing really changes, nor is there any type of fusion occurring. Choice (2) looks like a typical chemical reaction with Carbon bonding to Oxygen to make Carbon Dioxide.  We've never heard the term fusion in these types of typical reaction and (2) is probably an unlikely answer.  Choice (3) shows two Hydrogen atoms combining into each other to make a new element He. This looks like something that could be fusion.  But to be sure, look at (4).  This answer choice looks like a nuclear reaction where Uranium adds a neutron and then breaks itself into two separate elements.  Even if you didn't understand fusion thoroughly (3) looks like a better answer because to elements are joining together to make a new element rather than One splitting into two.  (3) becomes your best answer.

Correct Answer:

Answering the Question:

In order to answer this question it is important to understand what the result of β decay will be and how it occurs. According to Table N, N-16 will undergo β^- decay. This means that an electron will leave its nuclei creating an additional proton in the process. The concept of an electron leaving the nucleus of an element is a difficult concept to grasp. It is believed that the electron will be released as a result of the breakdown of a neutron to form a proton and an electron. This will lead to an increase in the atomic number from 7 to 8. However, since the proton was a result of the decay of a neutron the mass number will remain the same, as the mass number is the total number of protons plus the number of neutrons. The change in atomic number results in the formation of a new element with atomic number 8, which is O-16.