Why do atomic masses of most of the elements in atomic mass units involve fractions?

Why are atomic mass of some elements are in fractions?

What is atomic mass unit (amu)?

What is atomic mass unit (amu) ?

In each of the following question, an Assertion (A) is following by a corresponding Reason (R ). Use the following keys to choose the appropriate answer. Assertion : Average atomic mass of an element depends upon the atomic masses of different isotopes and their fractional abundances. Reason : Average atomic mass is obtained by multiplying the atomic mass of the heavier isotope with its fractional abundances.

Which of the following is not a merit of Mendeleev's original periodic table? a) Prediction of undiscovered elements and their properties b) Correction of atomic masses of a few elements c) Systematic arrangement of elements based on atomic mass d) Similar elements were placed in different groups e) Separate positions are given for isotopes f) Order of increasing atomic weight is not observed. The correct code is

What do we call the atoms of different elements with same mass number

Atoms have very very small mass and so usually the masses of atoms are given relative to a standard called atomic mass unit. What is Atomic Mass unit (AMU)?

If the average atomic mass of an element having two isotopes is 71, the ratio of the natural abundance of the two isotopes of mass 70 and 74 will be

The mass of an atom is expressed in

Calculate the atomic mass of an element which crystallises into a cubic structure with one atom on each corner of the cube. The volume of the unit cell is 24xx10^-24 cm^3 and density is 7.2 gcm^-3 .