Question

Define elements , compound and mixture , atomic mass ,atomic number ,Isotops​

Answer 1

Answer:

Since 1961 the standard unit of atomic masshas been one-twelfth the mass of an atom of the isotope carbon-12. An isotope is one of two or more species of atoms of the same chemical element that have different atomic mass numbers (protons + neutrons).

Explanation:

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Answer 2

Answer:

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Since 1961 the standard unit of atomic mass has been one-twelfth the mass of an atom of the isotope carbon-12. An isotope is one of two or more species of atoms of the same chemical element that have different atomic mass numbers (protons + neutrons).

... for example

Atomic weight.

element calcium

symbol Ca

atomic number 20

atomic weight 40.078