Chemistry Chapter 1.1 and 1.2

Question 1

What is a summary of Dalton’s Atomic Theory?

Answer 1

• Everything is made of the particles which is the smallest unit of matter (atom)
• All atoms are identical for each element
• Atoms of different elements form in specific ratios to make compounds
• In a chemical reaction, atoms are separated and reformed to make new compounds

Question 2

What was wrong with Dalton’s Atomic Theory?

Answer 2

• He didn’t account for subatomic particles

- Not all atoms are the same because of them

Question 3

Describe the cathode ray tube by Joseph John Thomson

Answer 3

Sealed glass tube + cathode beam (modified Crookes’ Tube)
Anode plate in the middle
He used many gases and metals as the beam

Question 4

What did the cathode ray tube lead in discovery?

Answer 4

The cathode beam deflected towards the anode plate meaning it was negative. A positive magnet attracted the beam, while a negative repelled it. It contained electrons.

Question 5

Describe Thomson’s model of the atom

Answer 5

Plum Pudding Theory:
Electrons remained in a positively charged spongy mass. The electrons repelled each other but were attracted the positive mass.

Question 6

Describe Rutherford’s gold foil experiment.

Answer 6

Really fast alpha rays are targeted at gold foil (gold atoms). They were supposed to just pass through, but instead some deviated in large angles, and some bounced completely back.

Question 7

Why were the results of the gold foil experiment unexpected. Explain Rutherford’s theory of atomic structure.

Answer 7

They were supposed to just pass through, but instead some deviated in large angles, and some bounced completely back. This meant that while the majority of an atom is empty space, the nucleus is a mass in the center with a positive and neutral center that when hit, caused the bounce back.

Pass through - Mostly empty space
Deflect - Nucleus is positive and so is the alpha ray
Bounce Back - Nucleus accounts for most of an atom’s mass

Question 8

Notation of an Element

Answer 8

Mass # Charge
Element Symbol
Atomic #

Question 9

How do you find each part of an element’s notation?

Answer 9

Atomic # - Number of protons
Mass # - Neutrons + protons
Charge - Number of electrons (2+ = two more electrons than protons)

Question 10

How do you find atomic mass of isotopes?

Answer 10

(Mass Element 1 amu)(% abundance) + (Mass Element 2 amu)(% abundance) + (Mass Element 3 amu)(% abundance)

Question 11

What should you never forget in calculations?

Answer 11

Units!

Question 12

How do you find the % abundance of an element?

Answer 12

(x)(Mass Element 1 amu) + (1-x)(Mass Element 1 amu) = Atomic Mass

Question 13

Describe how radiant energy that is quantized is fundamentally different that radiant energy that travels as waves.

Answer 13

• Quantized energy is in the form of whole number packets, and form straight lines when emitted.
• Waves are continuous gradients like rainbows

Question 14

State Bohr's postulates regarding the behavior of hydrogen's electron. 
Define:
- Stationary states
- Quantum Number
- Ground States 
- Excited States

Answer 14

• Certain allowed energy levels (stationary states) that correspond to a circular electron orbit of a fixed size (n = integer #)
• Larger orbit, greater energy
• n is a quantum number (1 to ∞)
• Lowest energy is the ground state (n = 1)
• Higher energy states are excited states ( n = Z < 1)
• If an electron moved in a stationary state, the atom did not radiate or absorb energy
• The electron can only move orbits if it absorbed or emitted and amount exactly equal to the energy difference between two orbits. (one state to another)