Rutherford's Experiments

Question 1

True or False: By the early 1900s, scientists had some understanding of the charge & mass of the negatively charged subatomic particles (electrons)

Answer 1

True

Question 2

In 1904, English physicist J.J. Thomson proposed what model of atoms?

Answer 2

The plum pudding model of atoms

Question 3

What was the purpose of the plum pudding model of atoms?

Answer 3

Described a positively charged mass with an equal amount of negative charge in the form of electrons embedded in it

Question 4

What major development in understanding the atom did Ernest Rutherford originate?

Answer 4

Rutherford performed a series of experiments using a bean of high-speed, positively charged alpha particles (a particles) that were produced by the radioactive decay of radium

Question 5

What do alpha particles (a particles) consist of?

Answer 5

Two protons and two neutrons

Question 6

What was Rutherford’s conclusions on the gold foil experiment?

Answer 6

Most of the a particles passed through the gold atoms undeflected meaning they must have traveled through essentially empty space inside the atom.

Question 7

True or False: Like charges repel each other

Answer 7

True

Question 8

What charge to alpha particles have?

Answer 8

Positive

Question 9

What were the two main conclusions from the gold foil experiment?

Answer 9

1. The volume occupied by an atom must consist of a large amount of empty space.
2. A small, relatively heavy, positively charged body, the nucleus, must be at the center of each atom.

Question 10

What did Rutherford’s gold foil conclusions lead to?

Answer 10

His proposal of a model in which an atom consists of a very, small positively charged nucleus in which most of the mass is concentrated with it being surrounded by negatively charged electrons, therefore making the atom neutral.

Question 11

What subatomic particle did Rutherford find and name?

Answer 11

Proton

Question 12

When are the a particles deflected in Rutherford’s gold foil experiment?

Answer 12

The a particles are deflected only when they collide with or pass close to the much heavier, positively charged gold nucleus.

Question 13

How was Rutherford’s gold foil experiment carried out?

Answer 13

Performed by aiming a particles at a sheet of gold foil and observing whether the a particles passed through, deflected slightly, or deflected significantly.

Question 14

What is true of the a particles that deflected?

Answer 14

This was an indication that a small region of positive charge existed to repel the positively charged a particles

Question 15

What is true of the a particles that went undeflected?

Answer 15

This indicated that the atom existed mostly of empty space

Question 16

What is a nucleus?

Answer 16

Massive, positively charged center of an atom made of protons and neutrons

Question 17

Why did Rutherford and his team choose gold foil?

Answer 17

Gold foil is very malleable. It could be hammered to approximately 10 nm thick and remain strong.

Question 18

Which of the following statements is false concerning Rutherford’s gold foil experiment?

A. Alpha particles aimed at the gold foil traveled at high speed
B. Some alpha particles were reflected back towards the source
C. Gold was chosen because it can be pounded very thin
D. It was found that an atom is mostly empty space.
E. Alpha particles were deflected once for every 100 particles.

Answer 18

E