ATOMIC THEROY

Question 1

atom:

Answer 1

the smallest unit into which matter can be divided without the release of electrically charged particles
*also known as the smallest piece of a pure substance

Question 2

Who discovered the atom?

Answer 2

-Democritus (400 BC) proposed that if a pure substance were divided into smaller pieces, eventually we would arrive at something so small it would be divided no further

Question 3

Who discovered the “Billiard Ball Model”?

Answer 3

-John Dalton (1808) proposed the 1st modern model of the atom

Question 4

Does Dalton’s model have internal parts?

Answer 4

-no because they are featureless spheres

Question 5

When are compounds created?

Answer 5

-when atoms of different elements join together in definite properties (ex. H20)

Question 6

What does John Dalton’s Model explain?

Answer 6

• it explains why “chemical reactions” occur in definite properties
• also explains “thermal properties” of matter such as pressure an temperature

Question 7

What does the “Billiard Ball Model” not explain?

Answer 7

• it does NOT explain the “electrical properties” of matter

* matter has positive (+) & negative (-) parts

Question 8

Who performed experiments to discover the “Raisin Bun Model” (Plum Pudding) ?

Answer 8

-J.J Thomson performed experiments (1897) to see how positive and negative matter were affected by electric and magnetic force

Question 9

Does positive or negative parts have smaller mass?

Answer 9

-the negative parts of matter have much smaller mass than the positive parts

Question 10

Which positive or negative part depend on the element?

Answer 10

-the mass of the positive parts depend on the element (same as Dalton’s model)

Question 11

Which part will always be the same?

Answer 11

-the negative parts will always be the same; regardless of which element the negative part came from

Question 12

What are the negative parts called?

Answer 12

-they are called “electrons”

Question 13

What are the positive parts called?

Answer 13

-they are called “protons”

Question 14

When was the “Raisin Bun” or “Plum Pudding” proposed?

Answer 14

-in 1904

Question 15

What does the “Raisin Bun Model” contain?

Answer 15

-the “bun” is a sphere containing most of the atom’s mass

(like the “Billiard Ball”, the size and mass of the atom differ from 1 element to another

Question 16

What are embedded in the “Raisin Bun Model”?

Answer 16

-there are “electrons” (raisins) embedded in the atom (bun) that have very small mass and a negative charge

Question 17

Do electrons have all the same properties in the “Raisin Bun Model”?

Answer 17

-different elements have differing numbers of electrons, but the electrons all have the same properties regardless of which element they came from

Question 18

Who discovered a “thin gold foil”?

Answer 18

“Ernest Rutherford” and his students performed an experiment (1909) where they fired small, high-speed, positive particles at a thin gold foil (“gold” is a large atom)

Question 19

What are the “alpha particles” passed through?

Answer 19

-most of the “alpha particles” pass through the gold foil with nearly no effect

Question 20

How many “alpha particles” are deflected by the gold foil?

Answer 20

-a very small percentage

Question 21

What did Rutherford conclude?

Answer 21

-he concluded that the “Raisin Bun Model” could not explain the results he had

Question 22

Who discovered the “Planetary (Nuclear) Model?

Answer 22

“Ernest Rutherford” proposed a new model (which is also called the “solar system” or nuclear model) (1911)

Question 23

What is Rutherford’s model mostly made up of?

Answer 23

-most of the atom is empty space, since the alpha particles were unaffected

Question 24

What is most of the atom’s mass in the Rutherford’s model?

Answer 24

• most of the atom’s mass is concentrated in a tiny nucleus, which cause some of the alpha particles to deflect

Question 25

What do the electrons orbit around in the Rutherford’s model?

Answer 25

-the electrons orbit around the nucleus like the planets orbiting the Sun

Question 26

protons:

Answer 26

have a positive charge (+)

Question 27

neutrons:

Answer 27

have no charge (-)

Question 28

What have nearly the same mass?

Answer 28

-protons and neutrons