The amount left after 20 years = 154.15 mg
<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.
The main particles are emitted by radioactive elements so that they generally decay are alpha (α), beta (β) and gamma (γ) particles
The decay formula for isotope :

Then for t=20 years, the amount left :

Answer:
it is burning of dry leaves in the garden
Answer:
periosteum, compact bone, cancellous, bone marrow
Upper N upper H subscript 4 upper C l (s) right and left arrows stacked above each other upper N upper H subscript 3 (g) plus upper H upper C l (g)
Explanation:
The given equation is;
NH₄Cl ⇄ NH₃ + HCl
This equation is clearly different from the other ones.
- In the reactant going forward, there is a right and left arrows stacked above each other.
- The symbol is ⇄ and it is used to show reversibility of chemical reactions.
learn more:
Chemical reactions brainly.com/question/3953793
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