Answer:
Protons and Neutrons
Explanation:
The sum of number of protons and the number of neutrons is equal to the mass of an element. Mathematically, it can be given as :
M = P + N
Also, the atomic mass can be calculated by the sum of the element's isotopes as isotopes have slightly different mass numbers.
Hence, protons and neutrons add together to determine the atomic mass.
Answer:
A = 349 g.
Explanation:
Hello there!
In this case, since the radioactive decay kinetic model is based on the first-order kinetics whose integrated rate law is:

We can firstly calculate the rate constant given the half-life as shown below:

Therefore, we can next plug in the rate constant, elapsed time and initial mass of the radioactive to obtain:

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