Answer:
Cabon-12 has same average atomic weight and mass number.
Explanation:
carbon-12 has average atomic weight 12 amu and mass number of 12.
amu represents average of mass of a nucleon.
As carbon-12 has same average atomic mass and mass number therefore carbon-12 is a good standard to determine average mass of a nucleon.
Again, abundance of carbon-12 isotope is almost equal to 99%. Therefore fluctuation of average atomic weight from 12 amu is very very low.
So, carbon-12 is taken as a standard to determine mass of a nucleon.
Hence atomic mass of carbon-12 is 12 amu.
It is a molecule because hydrogen is an element.
An element is made up of molecules
Answer:
2.5% of the earth's fresh water is unavailable: locked up in glaciers, polar ice caps, atmosphere, and soil; highly polluted; or lies too far under the earth's surface to be extracted at an affordable cost.
Explanation:
Answer:
Considering the half-life of 10,000 years, after 20,000 years we will have a fourth of the remaining amount.
Explanation:
The half-time is the time a radioisotope takes to decay and lose half of its mass. Therefore, we can make the following scheme to know the amount remaining after a period of time:
Time_________________ Amount
t=0_____________________x
t=10,000 years____________x/2
t=20,000 years___________x/4
During the first 10,000 years the radioisotope lost half of its mass. After 10,000 years more (which means 2 half-lives), the remaining amount also lost half of its mass. Therefore, after 20,000 years, the we will have a fourth of the initial amount.
