P1.1 - The Particle Model

Question 1

Which Greek philosophers first thought of the atom?

Answer 1

Democritus and Leucippus

Question 2

What does atomos mean in Greek?

Answer 2

Indivisible

Question 3

What did the Greek philosophers believe about the atom

Answer 3

It was too small to see

Eventually you could not cut up paper anymore and you would get an atom

Question 4

In What year was Dalton doing his experiment?

Answer 4

1870s

Question 5

What experiment was Dalton doing?

Answer 5

He was doing experiments to measure how elements combined

Question 6

Describe daltons model

Answer 6

A very small indestructible sphere

Question 7

What did Dalton think about atoms

Answer 7

All atoms in one element are the same

The atoms in one element are different from the atoms in all other elements

Question 8

When was Thomson investigating cathode rays

Answer 8

In 1897

Question 9

What did Thomson discover

Answer 9

He discovered an electron and found out that it had a negative charge

Question 10

What did Thomson find out about the atom?

Answer 10

An atom contains negative electrons

Overall atoms have no charge. They are neutral

Question 11

When did Thomson suggest his new model

Answer 11

In 1904

Question 12

What was the name of Thomson’s new model

Answer 12

The plum-pudding model

Question 13

Describe the plum pudding model:

Answer 13

The atom consists of a positive mass (like a cloud) with negative electrons embedded in it.

Question 14

How does the history of the atom link to idea change

Answer 14

The history of the model of the atom shows that ideas change when there is new evidence that cannot be explained using old ideas

Question 15

In what year was the Rutherford model discovered

Answer 15

1899

Question 16

What was Rutherfords experiment

Answer 16

They fired a

Question 17

Describe Rutherfords Experiment

Answer 17

He decided to fire alpha particles at a piece of gold foil

The alpha particle source was in a lead box with a narrow hole white a fixed thin metal foil placed in front of it.

The apparatus above was in an evacuated chamber to prevent air molecules absorbing the alpha particles

There was a detector outside of the chamber and everytime an alpha particle hit the glass plate, there was a spot of light.

The detector was moved to different positions and they counted the number of spots of light that they saw.

Question 18

Describe Rutherfords model of the atom

Answer 18

An atom is made up of a tiny positively charged nucleus with electrons around the outside.

Almost all of the mass of an atom is in its nucleus

Question 19

What was the problem with the plum pudding model

Answer 19

You would expect the electrons to spiral until they hit the nucleus

Question 20

Describe Bohrs model

Answer 20

Electrons can only move in fixed orbits called electron shells around the nucleus

Question 21

How big is an atom

Answer 21

1 ✖️10^-10

Question 22

What is an order of magnitude

Answer 22

Anything to the nearest power of 10

Question 23

How do you calculate the length of a molecule

Answer 23

Number of atoms ✖️10^-10 m/atom