Answer: Between 1 and 2.
Explanation:
Half life is the amount of time taken by a radioactive material to decay to half of its original value.
............(1)
where,
a = amount of reactant left after n-half lives = 40
= Initial amount of the reactant = 100
n = number of half lives
Putting in the values we get:

taking log on both sides


Thus half-lives that have elapsed is between 1 and 2
I believe it is A because the plant is offering protection while the bacteria is converting it in to nitrogen that the plant can use!
SiO2 is the only possible choice because the other formulas contain metals. how do we know this? because the other formulas contain elements located on the left of the “staircase” on the periodic table that separates metals from non-metals.
Possibly C or D i wanna say sorry if i’m wrong
Answer:
Nonbonding pairs of electrons.
Explanation:
Both oxygen atoms in the diatomic molecule have two nonbonding pairs. This results in the oxygen molecule having a planar geometric shape. This is because nonbonding pairs repel each other are significant in determining the shape of a molecule.