Components and Theory of Atoms

Question 1

Who performed a number of experiments reacting atmospheric gases that result in NO2 and NO3 with no compound in between?

Answer 1

John Dalton

Question 2

What are the 4 building blocks that Dalton used to describe “small indestructible spheres” called atoms?

Answer 2

1. All matter is made of atoms
2. Atoms of the same element have the same average mass, size and unique properties
3. Atoms cannot be converted into atoms of another element through chemical reactions
4. Atoms of different elements combine in specific proportions to form compounds

Question 3

Who proposed the Plum Pudding Model (Blueberry Muffin Model) where electrons can be stripped from a soft positively charged atom?

Answer 3

Joseph Thompson

Question 4

Explain the process and key inferences in the “Plum Pudding Model”

Answer 4

Process:
•cathode ray tubes create a beam of small particles that make a flash of light when aimed at a screen
•charged plates are placed on either side of the beam to determine the charge of the particles

Observations/Inferences:
•beam of particles deflected towards the positive plate
-inference: beam must contain negative particles since opposites attract. since atoms are neutral, they must contain electrons that can be removed from a positive material

Question 5

Who used the “Gold Foil Experiment” to prove their model? (shooting positively charged particles at a thin piece of gold foil)

Answer 5

Ernest Rutherford

Question 6

Explain the observation and overall atomic model of Ernest Rutherford

Answer 6

Observations:
•most particles went straight through the gold foil but some deflected back towards the particle gun
•later exploded nuclei and observed positive particles

Atomic Model:
•atoms have a small dense positive nucleus with electrons travelling around it

Question 7

Explain the issue with Rutherford’s Model

Answer 7

electrons orbiting the nucleus would get attracted to the nucleus composed of positively charged particles because of opposite charge attraction. the electrons would quickly spiral into the nucleus and cause a nuclear explosion (explained by bohr)

Question 8

Who’s model applies the ideas of transferring energy in specific amounts and that light is packets of energy (photons) ?

Answer 8

Niels Bohr

Question 9

Why must electrons only have a certain amount of energy, according to Bohr?

Answer 9

each orbit has a required amount of energy in order for stay the electrons to stay in orbit around the nucleus.

Question 10

Explain the 3 rules that electrons follow when travelling around the nucleus, according to Bohr

Answer 10

1. electrons have specific allowable energy levels that represent fixed, circular orbits around the nucleus
2. while in orbit, electrons do not gain or lose energy
3. an electron can change orbits by emitting or gaining energy that is exactly equal to the difference between the 2 orbits

Question 11

What happens when atoms are heated, according to Bohr?

Answer 11

When heated, electrons gain thermal energy and transforms it into kinetic energy. This requires a larger radius for the electron to follow around the nucleus, forcing the electrons to jump to a higher orbit. Electrons are more unstable in higher orbits so, it will reduce its speed by releasing kinetic energy to drop down to the lowest possible orbital. This emits light! Light can be calculated into wavelength unit which associates with its own unique colour! but only for atoms that have 1 electron

Question 12

What is an real life example of Bohr’s atomic model?

Answer 12

fireworks use different elements to create different colours when exploded in the air. for example, a yellow firework is a Na (sodium) atom that, when heated, forced the electron to jump up and then down and released energy to create light!

Question 13

Who discovered the presence of neutrons in the nucleus?

Answer 13

Rutherford

Question 14

What was Rutherford’s experiment in 1920 that evoked the introduction of neutrons in the nucleus?

Answer 14

he calculated the mass of protons that it would take to balance the electrons in the atom, but the actual atoms weighed significantly more than his calculations.
This meant that there must have been another particle in the nucleus to account for the missing mass. It had to be a neutral charge so that it didn’t upset the charge balance in the atoms.

Question 15

What was Rutherfords latest conclusion of the atomic model?

Answer 15

the nucleus of an atom contains protons and neutrons with electrons travelling around the nucleus in Bohr’s orbits.

Question 16

Who explained the existence of electrons and what was their experimental evidence to support it?

Answer 16

Thompson initially discovered electrons through his cathode ray experiment where the particles deflected towards the positively charged plate which signified their negative charge (opposite charge attraction). But, he believed that atoms were positively charged spheres with embedded electrons, whereas, Bohr discovered that electrons instead travel around the nucleus. He was very successful at mathematically predicting the amounts of energy that electrons actually travel at around the nucleus (electrons have specific energy levels in order to follow their fixed, circular orbits around the nucleus. Finally, schrödinger applied de Broglie’s wave theory to Bohr’s model to determine the position of an electron with each of Bohr’s energy levels. He derived the schrödinger wave equation to predict the location of an electron over time using statistical probability (creating regions of probability orbitals with 95% accuracy)

Question 17

Who explained the existence of protons and what was their experimental evidence to prove this?

Answer 17

Rutherford discovered the presence of protons in the nucleus through his gold foil experiment when some positive particles deflected back towards the particle gun. This signified the presence of a dense positive structure that the positive particles were repelled off due to same change repulsion. If the nucleus was negatively charged, the positive particle would have hit and stuck to it and caused a disappearance of it completely. Also, the positively charged nucleus caused the positive particles to flee from the centre line instead of attracted to it, like with the negatively charged nucleus.

Question 18

Who explained the existence of neutrons and what experimental evidence do they have to prove it?

Answer 18

Rutherford discovered the existence of neutrons in the nucleus when he calculated the mass of protons to balance the electrons in an atom but the actual atoms weighed significantly more than this calculations. This indicated that there must be another particle in the nucleus to account for the extra mass. And since there has to be a neutral charge so that there is no disruption between the balance in the atoms, the charge of the extra mass must be neutral. Therefore, the nucleus of an atom contains protons and neutrons while electrons travel around the nucleus in Bohr orbits.
Also, Chadwick proved this theory through experimentation later on.