Question

Section 2.3 describes the postulates of Dalton's atomic theory. With some modifications, thesepostulates hold up very well regarding how we view elements, compounds, and chemicalreactions today. Answer the following questions concerning Dalton's atomic theory and themodifications made today.
a. The atom can be broken down into smaller parts. What are the smaller parts?
b. How are atoms of hydrogen identical to each other, and how can they be different from eachother?
c. How are atoms of hydrogen different from atoms of helium? How can H atoms be similar to Heatoms?
d. How is water different from hydrogen peroxide $\left(H_2{O}_2\right)$even though both compounds arecomposed of only hydrogen and oxygen?
e. What happens in a chemical reaction, and why is mass conserved in a chemical reaction?

Short answer

Protons, Neutrons and electrons are the smallest particles.

Step-by-step solution

Smaller parts when the atom can be broken down into smaller parts

Assumptions are made according to the atomic theory, which is totally contradicted to the theory of Modern atoms. The smallest particle are unable to divide further. It can only be divided according to modern atomic theory. Thus, smaller particles are Protons, electrons and neutrons.

Atom identical to each other

The elements of same atom having similar properties which are come from same element according to the atomic model. The theory of modern atom proves that the atoms come from same element are different. These properties are respect to isotopes.

Atoms of hydrogen different from atoms of helium and H atoms similar to He atoms

The hydrogen atom are different from helium, because of atomic weight of helium is 4 whereas for hydrogen is 1. The same property between helium and hydrogen is 1g of H. Both Hydrogen and Helium constitute$6.023\times {10}^{23}$atoms.

Water different from hydrogen peroxide H2O2 even though both compounds are composed of only hydrogen and oxygen

The Hydrogen peroxide and water compounds are different in their bonding. Water contains bond of O-H whereas hydrogen peroxide has O-O bond and also O-H bond. The molecular weight also different of these two compounds.

Conversion of mass in the chemical reaction

There is an atom rearrangement from the reactant to the product in chemical reaction for getting the new products. There is a mass conservation in chemical reaction due to their involvement in atoms rearrangement. The total mass of reactants and products are equal.