So what am I suppose to answer here?
Answer:
B is the correct answer I say
Cs -137 has a half life of about 30 years. If 60 years pass, there is two half lives passed so 1/2 * 1/2= 1/4. Take 1/4 and multiply it with the mass given:
(1/4)*20mg=5mg left
There are two subshells that are s and p, which are present in the second energy level.
The energy level can be defined as the fixed distances from the nucleus of an atom where electrons may be found. Each energy level is divided into some Subshells. These subshells are known as s-subshell, p-subshell, d-subshell, and f-subshell. This subshell contains some orbitals, these orbitals are the place where there is the maximum probability of getting the electrons. In one orbital, a maximum of two electrons can be present.
Hence, there are two subshells in the second energy level.
Learn more about subshells here:
brainly.com/question/26438203
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