Answer:
your question is incomplete and its
particles which is one mole of a substance
Explanation:
you can solve the question by using this formular 1 mole of a substance=mass of the substance/ its molar mass
you find molar mass of a compound by adding individual molar masses of elements in that compound
Every 2 million years the amount is halved
0 million = 200g
2 million = 200g/2 = 100g
4 million = 100g/2 = 50g