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 think it’s 7.41 because you count up all the atoms and find out how many are x (the large grey ones) and you do 2/27 x 100 which gives you 7.41 :) (sorry if i counted wrong it’s kinda hard)
Answer:
no
Explanation:
A compound is a material formed by chemically bonding two or more chemical elments.
Molecules is the answer i believe
Most solids a) are dense and difficult to compress.
Most solids are closely compacted, their molecules are close together and vibrate. They don't move freely like gas or water molecules do.
They are difficult to be squeezed or flattened.