Which of the following is not part of Atomic theory?
A.) Compounds are made up of combinations of atoms
B.) All atoms of the given element are alike
C.) All matter is composed of atoms
D.) A chemical reaction involves the rearrangement of atoms
E.) The atom is mainly empty space

Hint: You should know that in chemistry, atomic theory is a scientific theory of the nature of matter, which states that matter is composed of discrete units called atoms. Now, try to solve this question.

Complete step by step answer:

Atomic theory was given by John Dalton in 1808. Dalton's atomic theory was the first complete attempt to describe all matter in terms of atoms and their properties.
This theory was based on the law of conservation of mass and the law of constant composition.
Here are the postulates of Dalton’s atomic theory -
All matter consists of indivisible particles called atoms.
Atoms of the same element are similar in shape and mass but differ from the atoms of other elements.
Atoms cannot be created or destroyed.
Atoms of different elements may combine with each other in fixed, simple, whole-number ratios to form compound atoms.
Atoms of the same element can combine in more than one ratio to form two or more compounds.
The atom is the smallest unit of matter that can take part in a chemical reaction.
So, we can say that the option E “The atom is mainly empty space” is not a part of the atomic theory.
Therefore, the correct answer to this question is option E.

Note: We should know that atoms are not mostly empty space because there is no such thing as purely empty space. Rather, space is filled with a wide variety of particles and fields. Even if we ignore every kind of field and particle except electrons, protons, and neutrons, we find that atoms are still not empty.