Question

1. Which of the following is not part of Dalton's atomic theory?

A. Atoms cannot be divided created or destroyed
B. The number of protons in an atom is its atomic number
C. In chemical reactions, atoms are combined, separated, or rearranged.
D. All matter is composed of extremely small particles called atoms

2. Daltons atomic theory agrees with modern atomic theory except for the statement that
A. All matter is made up of small particles
B. Atoms are not divided in chemical reactions
C. Atoms of the same element are chemically alike
D. All atoms of the same element have the same mass

3. When an electrical current passed through a glass tube, it caused the surface of the tube directly across from the cathode to glow. Scientists concluded that...
A. A magnetic field was produced
B. The particles of the beam were negatively charged.
C. There was gas in the tube
D. Atoms were indivisible

Answer 1

Step-by-step explanation:

1. B. The number of protons in an atom is its atomic number

The crux of the Dalton's atomic theory is that atoms are the smallest indivisible particle of any matter. Beyond the atom, no other smaller particles exist. This has been proven wrong by the discovery of subatomic particles such as protons, neutrons and electrons.

2. D. All atoms of the same element have the same mass

The discovery of isotopes nullifies this claim. An atoms mass is a function of the number of protons and neutrons it contains. These particles are called nucleons and they are located in the tiny nuclear space of the atom.

In isotopes, an atom can exist in two or more ways with each having the same atomic number but different mass numbers due to difference in the number of their neutrons.

Isotopes are still chemically alike i.e they have the same number of electrons and protons for a neutral atom but their number of neutrons differs.

3. B. The particles of the beam were negatively charged.

This is the experiment conducted by Sir J.J Thomson on cathode ray tubes. This lead to the discovery of electrons called cathode rays as a subatomic particle.

One of the properties of the rays is that "the particles of the beam produced in the tube are negativey charged and they attract positive charges". The rays originates from the cathode and moves towards the positively charged anode.