The discovery and characterization of cathode rays was important to the development of atomic theory because
1. it led to the suggestion of the existence of the neutron.
2. it indicated that all atoms contain pro- tons.
3. it indicated that all atoms contained elec- trons.
4. it indicated that all atoms contain α particles.
5. it provided a basis for weight calculations in chemical changes

3. it indicated that all atoms contained elec- trons.

Explanation:

J.J Thomson made the following conclusions after experimenting with the cathode ray tubes:

- The cathode ray is composed of negatively-charged particles.

- The particles must exist as part of the atom, since the mass of each particle is only 1/2000 the mass of a hydrogen atom.

- These subatomic particles can be found within atoms of all elements.

Due to the folling conclusions above, we can say that option 3 is the correct option bacause the properties of an electron meets the conclusion of Thompson.

what are the two models

explanation:

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.