Question

What are the two most abundant elements in the solar system? How much of the mass of the solar system do they make up?

2) 3a. When a rock is formed, it has 1000 atoms of radioactive 14C. At a later time, it only has 250 atoms of 14C. How many half-lives have gone by?

3)

Answer 1

1) 99.9% of the mass of the solar system is sun. So, the most abundant elements in the solar system will be the main constituents of the sun.

Since sun is a star, the most important element in it will be hydrogen (it is the fuel in all stars). Almost 75% of sun is hydrogen. The energy is produced in the sun by converting hydrogen into helium. So, the next main constituent of the sun, and thus of solar system is Helium. almost 25% of the solar system is helium.

All other components in the solar system constitute only 0.1%.

2) Half life of an element is the time it takes for it to become half its initial value.

Here, initially, there are 1000 atoms. After one half life, it becomes 500 atoms. After the second half life the no of particles will become 250 and so on.

Here, after the time t, the no of atoms has reduced to 250. So, the no of half lives passes is 2.