Because they often have long half-lives, their radioactive persistence in the environment is lengthy.
Number 4
If you spot any errors in my English, please tell me, since I am not a native speaker.
Answer: Copper is being oxidized and acts as a reducing agent. In contrast, silver is being reduced, functioning as the oxidizing agent.
Explanation:
An oxidation reaction involves the loss of electrons by an atom. Here, the oxidation state of the atom rises.

Conversely, a reduction reaction is characterized by an atom gaining electrons, resulting in a decrease in its oxidation state.

Oxidizing agents are those that facilitate the oxidation of another substance while themselves being reduced. These substances participate in reduction reactions.
Reducing agentsare defined as those that reduce other substances while undergoing oxidation themselves. They also take part in reduction reactions.
In the provided chemical reaction:

The associated half-reactions for the above process are:
Oxidation half reaction: 
Reduction half reaction: 
From the reactions outlined, copper is losing electrons. Consequently, it is oxidized and regarded as a reducing agent.
Silver is acquiring electrons, thus it is being reduced and viewed as an oxidizing agent.
The electronic configurations will be listed as follows. Electronic configuration refers to how electrons are arranged around an atom's nucleus. The number of electrons in an atom corresponds to its atomic number. The atomic number indicates how many protons or electrons are present in a neutral atom, meaning the atomic number equals the count of both protons and electrons. For manganese, its atomic number is 25, which equals the number of protons. Thus, the number of electrons, considering any charge, is 25 for a neutral manganese atom. In the case of the Mn atom, there are 25 electrons. The electronic configuration for Mn is specified as follows: For the Mn2+ ion, the number of electrons is 25 - (+2) = 23. For the Mn4+ ion, the count is 25 - (+4) = 21. For the Mn6+ ion, the total becomes 25 - (+6) = 19. Finally, for the Mn7+ ion, we have 25 - (+7) = 18. The electronic configurations are summarized above.
The chemical reaction involving oxygen, O2, and hydrogen, H2, yielding water can be represented as,
2H2 + O2 --> 2H2O
The masses of the reactants can be calculated as follows:[
2H2 = 4(1.01 g) = 4.04 g
O2 = 2(16 g) = 32 g
Considering we have 1.22 grams of oxygen, let's find out how much hydrogen is necessary.
(1.22 g O2)(4.04 g H2 / 32 g O2) = 0.154 g of O2
Since we have 1.05 grams of O2, this makes 1.22 grams of oxygen the limiting reactant.
Answer: 1.22 g of oxygen