What elements are present in water?

How many rare earth elements are present in the periodic table? Give an example.

What are transition elements? How many transition elements are present in the first transition series?

Transition elements are present in:

It is said that elemental composition of living organisms and that of inanimate objects (like earth's crust ) are similar in the sense that all the major elements are present in both. Then what would be the difference between these two groups ? Choose a correct answer from the following.

Which of the following element(s) is/are present in bronze?

‘All elements that are present in a plant need not be essential to its survival’. Comment.

How many elements are present in living organisms in form of various compounds?

All elements that are present in a plant need not be essential to its survival'. Comment.

The half-life of a radioactive element is 1600 y. After what time 10% of that element present in any radioactive sample will disintegrate?

How many mole of water molecules are present in 1.8 mL of water?