Radioactivity or radioactive decay is the process that occurs when unstable isotopes or atoms release energy by emitting radiations such as ,gamma radiations, alpha radiations and beta radiations to attain stability. Therefore, in this case decay is likely to occur when a given atom has two many neutrons in its nucleus in order to attain stability.
Electrons = protons
protons = atomic number
protons + neutrons = atomic mass
Therefore: a) protons + 7 = 15
protons= 15 -7
protons= 8
B) Remember proton = atomic number
so atomic number = 8
C)Now we know the atomic number so we can easily check on the periodic table what element has an atomic number of 8, which is Oxygen
from ICE table
H2(g) + I2 (g )↔ 2HI(g)
equ 0.958 0.877 0.02 first mix1
0.621 0.621 0.101 sec mix2
Kp1 = P(HI)^2 / p(H2)*p(I2) for mix 1
= 0.02^2 / 0.958*0.877
= 4.8x10^-4
Kp2 = P(HI)^2 / P(H2)* P(I2) for mix 2
= 0.101^2/ 0.621*0.621
= 0.0265
we can see that Kp1< Kp2 that means that the sec mixture is not at equilibrium. It will go left to reduce its products and increase reactant to reduce the Kp value to achieve equilibrium.
and the partial pressure of Hi when mix 2 reach equilibrium is:
4.8x10^-4 = P(Hi)^2 / (0.621*0.621)
∴ P(Hi) at equilibrium = 0.0136 atm
Answer: The empirical formula of the compound is 
Explanation:
Empirical formula is defined formula which is simplest integer ratio of number of atoms of different elements present in the compound.
Percentage of iron in a compound = 36.76 %
Percentage of sulfur in a compound = 21.11 %
Percentage of oxygen in a compound = 42.13 %
Consider in 100 g of the compound:
Mass of iron in 100 g of compound = 36.76 g
Mass of iron in 100 g of compound = 21.11 g
Mass of iron in 100 g of compound = 42.13 g
Now calculate the number of moles each element:
Moles of iron=
Moles of sulfur=
Moles of oxygen=
Divide the moles of each element by the smallest number of moles to calculated the ratio of the elements to each other
For Iron element = 
For sulfur element =
For oxygen element = 
So, the empirical formula of the compound is
