B. 11,540
<h3>Further explanation
</h3>
The atomic nucleus can experience decay into 2 particles or more due to the instability of its atomic nucleus.
Usually radioactive elements have an unstable atomic nucleus.
General formulas used in decay:

T = duration of decay
t 1/2 = half-life
N₀ = the number of initial radioactive atoms
Nt = the number of radioactive atoms left after decaying during T time
Nt=25 g
No=100 g
t1/2=5770 years

Because the formation of rust is a kind of chemistry reaction.
After chemistry reaction, compound with new properties is produced.
Of course, color is one of the new properties.
For example, if you put iron in colorless acid solution, a green solution is made.
This kind of chemisty reaction differs from physical reaction, for example, pigment with one color dissolves in liquid, a liquid with same color is made.
Answer:
The name of this compound is :
Bi2(CO3)3 = Bismuth Carbonate
Explanation:
The name of the compound is derived from the name of the elements present in it.
The rule followed while naming the compound are:
1. The first element (always the cation) is named as such .
2. The second element (The anion) end with "-ate , -ide ," etc
3. NO prefix is added while naming the first element.
For example : Bi2 can't be named as Dibismuth
Na2 = Can't be named as disodium
Hence the compound :
Bi2(CO3)3 contain two element : Bi and CO3. Here , Bi = cation (named as such) and CO3 = anion (named according to rules)
Bi = Bismuth
CO3 = carbonate
Bi2(CO3)3 = Bismuth Carbonate
The molecular mass of this compound is :
Molecular mass = 2 (mass of Bi) + 3(mass of C) + 6(mass of O)
= 2 (208.98)+3(12.01)+6(15.99)
= 597.987 u
Hey ik this isn’t a big help but there is a Chem app you can use to get your answers faster rather than waiting for someone to respond. anyways the app is called, ChemCalculator.
Hey there! The answer to your first question is SILICON, Nickle has 28 protons, silicon has 14, 14+14=28. Its the only element thats adds up. I dont know about the 2nd one myself.