Amount, when used as a noun, describes a quantity of uncountable nouns, such as air, water, or time.
When used as a noun, numbersignifies a quantity of countable nouns, such as trees, cities, or papers.
When is amount used?
When used a noun: For instance, We did not have sufficient amount of time to visit the park.
As a verb, amount is used with to (amount to); it describes an accumulation of something.
For instance, My bill amounted to $400.
When is Number used?
When used as noun:
For instance, I have to review a number of research papers today.Number is also used as a verb when you want to give a serial number to something or to count something that is typically large in numbers.
For instance, All the seats in the classroom are numbered.
Tips to Remember
Incorrect: We noted the amount of atoms present in 100g of sodium chloride.
Since ‘atom’ is a countable noun, using the word amount makes the sentence unidiomatic. The right word to use is number, and the correct sentence is:
Correct: We noted the number of atoms present in 100g of sodium chloride.