Option 4. ratio of electrons to protons
Isotope that has atomic number of 82 is stable. An element that has an atomic number ∠82 more stable except Tc and Pm. Also there is the concept that isotopes consisting a combination of even-even,even-odd,odd-even, and odd-odd are all stable. Many isotopes with no magic numbers of nucleons are stable
The answer is c Yep Allll day
When an iron is dipped in Copper Sulphate
Solution this reaction between them and
copper sulphate change into blue color to light
green color. This show that iron is more
reactive then copper, it can to replace copper
from CuSO4 , CuSO4 is of blue color and
FeSO4 is light green color.
Hope it helps
Answer : The balanced equation is,

Explanation :
According to the Bronsted Lowry concept, Bronsted Lowry-acid is a substance that donates one or more hydrogen ion in a reaction and Bronsted Lowry-base is a substance that accepts one or more hydrogen ion in a reaction.
The balanced chemical reaction will be,

In this reaction, hydrofluoric acid is act as a Bronsted Lowry-acid because it donate one hydrogen ion to
and
is act as a Bronsted Lowry-base because it accept one hydrogen ion from
.