Answer:
The nucleus of an atom contains the majority of the atom’s mass, and is composed of protons and neutrons, which are collectively referred to as nucleons. The much-lighter electrons orbit their atom’s nucleus. The Protons. Protons are positively charged particles found in an atom’s nucleus.
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The awnser is. 1728000 kilometers
Answer:
860.6 years.
Explanation:
The parameters given are;
Initial detector activity = 370000 alpha decays per second
Final detector activity = 93000 alpha decays per second
Formula for time to change in activity is given by the following relation;

t₉₃₀₀₀ = 2.72 × 10¹⁰ seconds = 860.6 years.
Answer:B
Explanation:
Option A:
In the nuclear reactions,neutron can be split into proton an electron.
In this case,the number of protons are increasing,increasing the atomic number.
Hence,the atomic number is not conserved.
Option B:
In any reaction the sum of number of neutrons and number of protons remain constant before and after the reaction.
Option C:
The mass number may change for the atoms.For example
emission reduces the atomic number by 
Option D:
In the nuclear reactions,neutron can be split into proton an electron.
So,they number of neutrons may change.