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 :]
A.)Calculate the mass of ammonium sulfate that would be obtained by reacting with ammonia acid.
<em>Correct me if i'm wrong :]</em>
There are 76 atoms in total
Answer:
<u>thermal conductivity:</u> the rate at which heat is transferred by conduction through a unit cross-section area of a material, when a temperature gradient exits perpendicular to the area
<u>electrical conductivity:</u> the measure of the amount of electrical current a material can carry or it's ability to carry a current
<u>solubility:</u> the ability to be dissolved, especially in water
<u>magnetism:</u> a physical phenomenon produced by the motion of electric charge, resulting in attractive and repulsive forces between objects
<u>melting point:</u> the temperature at which a given solid will melt.
<u>boiling point:</u> the temperature at which a liquid boils and turns to vapor
Explanation:
hope this helps :D pls mark brainliest :D