Hi me solve this questions1. after 38 days, all that is left of a 50g sample of an isotope is 0.0488 g. which isotope is this? (graph 1)2. how many more years will it take to have 0.625 grams of strontium-90(graph 2)true or false1. a radioactive alkaline earth metal belongs to group 8a of the periodic table after emitting an alpha radiation.

The radioactive decay follows first order kinetics

The integrated rate law expression for first order rate is

ln(A / At) = kt

Where A= initial concentration

At=concentration at time "t"

t = time

K= rate constant

ln(50 / 0.0488) = k X 38

Therefore

K = 0.1824 day-1

The relation between rate constant and half life is

So half life = 0.693 / 0.1824 = 3.8 days

So isotope must be Radon-222

it's c. elements are placed in rows based on how may valencies electrons have.

1. a)c-14 has two more protons

2. d)they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature.

3. c) iron and nickel.