Unit 2 - Atomic Concepts - History of the Atom - Regents

Question 1

What did Aristotle state in 384 BC? (2)

Answer 1

1. Matter is composed of 4 elements
2. Matter is continuous, not atomistic

Question 2

What term Leucippus and Democritus create in 450 BC?

Answer 2

Atomos

Question 3

What did Leucippus and Democritus picture atoms as?

Answer 3

Pictured atoms as round and smooth

Question 4

Definition of Atomos

Answer 4

1. Point at which
2. Matter can no longer be subdivided

Question 5

What did Lavoisier state in the early 1700s?

Answer 5

Substances can be made up of 2 or more elements

Fun Fact: Lavoisier stated that matter cannot be created or destroyed

Question 6

Law of Definite Proportions

Answer 6

Compound - Same unique elements are in definite proportions

Question 7

Law of Multiple Proportions (2)

Answer 7

1. Elements can join in different ways
2. Each way creates a unique substance with its own properties

Question 8

What is Dalton’s Theory? (4)

Answer 8

1. All matter is composed of atoms
2. All atoms in element are same & different from atoms in another element
3. Compounds are comb. atoms of diff elements IN FIXED PROPORTIONS
4. Chemical RXN = Rearrangement of Atoms

Question 9

What did they find out in the 20th century about the “Indivisible Atom”?

Answer 9

Made up of subatomic particles

Question 10

What did JJ Thomson determine in 1897? (7)

Discovered, Used, Determined

Answer 10

1. Discovered e-
2. Used the Cathode Ray Tube
3. e- have high charge - mass ratio
4. Atoms are divisible
5. p+ = e-
6. Matter is neutral
7. Plum Pudding - + charges evenly spread out & - charges in bits

Question 11

Plum Pudding Model?

Answer 11

Imagine a big, soft, spongy dessert like a plum pudding (or, in modern terms, a chocolate chip cookie). In this model, the pudding or cookie dough represents the positive charge, which is spread evenly throughout the atom. The chocolate chips (or plums) are the electrons, which are negatively charged particles scattered throughout this positive charge. The electrons are the “bits” within the atom.

This was Thomson’s idea of how the atom was structured before the discovery of the nucleus, which later models revealed was not quite right.

Question 12

What did Rutherford discover? (5)

Used, Discovered, Determined

Answer 12

1. Used the Gold Foil Experiment
2. Discovere nucleus
3. Atom’s mass is conc. in small + charges
4. e- is farthest away from atom
5. Atoms are mostly empty space

Question 13

What was Bohr’s contribution to chemistry? (4)

Answer 13

1. Created Planetary Model
2. e- revolve around nucleus
3. In Circular Orbits & Shells

Question 14

Definition of Orbitals (2)

Answer 14

1. 3D Space in Shells outside Nucleus
2. Where e- have high probability being found

Question 15

What is the Wave Mechanical Model (4)

Answer 15

1. Replaced Bohr Model
2. AKA e- Cloud/Modern Model
3. e- found 3D Orbitals
4. Each EL contains one or more orbitals

Question 16

Does each orbit have a definite energy? (3)

Answer 16

1. Yes in Proximity to Nucleus
2. Closest Orbit = Lowest E
3. Farthest Orbit = Highest E
   KID ON LEASH

Question 17

1. Atoms of the same elements are alike
2. Solid indivisible spheres

Answer 17

Dalton

Question 18

Matters’ made up of atoms

Answer 18

Democritus

Question 19

1. Discovered electrons
2. Plum Pudding Model
3. Cathode Ray Tube

Answer 19

Thomson

Question 20

1. Gold Foil Experiment
2. Discovers heavy, + charge nucleus
3. Mostly empty space

Answer 20

Rutherford

Question 21

1. Planetary Model of Electrons
2. Different Energies

Answer 21

Bohr