Answer : The time passed in years is 
Explanation :
Half-life = 5730 years
First we have to calculate the rate constant, we use the formula :



Now we have to calculate the time passed.
Expression for rate law for first order kinetics is given by:

where,
k = rate constant = 
t = time passed by the sample = ?
a = let initial amount of the reactant = X g
a - x = amount left after decay process = 
Now put all the given values in above equation, we get


Therefore, the time passed in years is 
Answer:
Chlorine (Cl)
Explanation:
The equation would be:
→ 
This is because no atom is lost in a reaction. Chlorine would be the missing chemical as it is on the other side of the equation and needs to be accounted for on the products side.
Answer:
P2N5
Explanation:
you have to plus it 2 times