Structure of an atom

Question 1

Definition of a model

Answer 1

Simple way of showing or explaining a complicated object or idea based on evidence.

Question 2

Definition of alpha particle

Answer 2

Particle with a positive charge given out by some radioactive elements - it is smaller than an atom.

Question 3

Definition of electrons

Answer 3

Very small negatively charged particles in an atom.

Question 4

Definition of neutrons

Answer 4

Particles with no charge in the nucleus of an atom.

Question 5

Definition of protons

Answer 5

Positively charged particles in he nucleus of an atom.

Question 6

Definition of a nucleus

Answer 6

The central part of an atom- contains protons and neutrons.

Question 7

Definition of plum pudding model

Answer 7

Early model of an atom- a cloud of positive charge with electrons embedded in it.

Question 8

Definition of shells

Answer 8

The paths or orbits that electrons move along in an atom.

Question 9

Definition of Periodic Table

Answer 9

How the elements are arranged in order of their atomic number.

Question 10

Name the scientist who showed that atoms contain negatively charged particles.

Answer 10

J.J. Thomson

Question 11

What did J.J Thomson call his negatively charged particle?

Answer 11

Electrons

Question 12

Why did J.J. Thomson assume that there also must be positively charged parts in an atom?

Answer 12

He assumed that there also must be positively charged parts in the atom because atoms are neutral- the opposite charges cancel each other out.

Question 13

Why was J.J Thomson’s model called the plum pudding model?

Answer 13

His model was called as the plum pudding model because the electrons seemed to be spread out in a cloud of positive charge. The electrons were like the plums and the rest of the atom was the pudding.

Question 14

Which particles were fired during the experiment carried out by Rutherford?

Answer 14

Small, fast moving alpha particles.

Question 15

What is the charge of the particles that were fired on the gold sheet?

Answer 15

The charge of the particles that were fired on the gold sheet was positive.

Question 16

What should be the observation, if the plum pudding model was correct?

Answer 16

If the plum pudding model was correct, the alpha particle should pass straight through the gold foil.

Question 17

What were the actual observations of Rutherford after bombarding the particles?

Answer 17

The actual observations of Rutherford after bombarding the particles were that most of the particles went through, but a few were deflected- some even bounced back.

Question 18

Describe the model of an atom suggested by Rutherford based on his evidence.

Answer 18

The model of an atom suggested by Rutherford based on his evidence was that the atom had a small, positively charged nucleus with the electrons arranged further away. He thought that the atom was mostly empty space.

Question 19

Explain how Rutherford’s new model was similar to the plum pudding model.

Answer 19

Similarities that the Rutherford’s model had with the plum pudding model :

1. They both had negative and positive charges.
2. They both described an atom in sphere shape.

Question 20

Explain how Rutherford’s new model was different from the plum pudding model.

Answer 20

Differences that the Rutherford’s model had with the plum pudding model were:

1. In the plum pudding model there was no nucleus, where as, the Rutherford model had a nucleus.
2. In the plum pudding model the electrons were embedded in a cloud of positive charge but in the Rutherford model there was a positively charges nucleus with electrons arranged further away.

Question 21

What is present in the nucleus of an atom?

Answer 21

Protons and Neutrons

Question 22

What is present in the shells of an atom?

Answer 22

Electrons

Question 23

Write the charges of the following particles:
Protons-
Electrons-
Neutrons-

Answer 23

Protons- Positive
Electrons- Negative
Neutrons- Neutral

Question 24

An atom does not have overall charges. Explain.

Answer 24

The atoms of an an element always have the same numbers of protons and electrons. This means that they have no overall charges- the opposite charges cancel each other out.

Question 25

What is meant by an atomic number of an atom ?

Answer 25

Atomic number of an atom is the total number of protons or electrons an atom of an element has.

Question 26

What is meant by a mass number of an atom?

Answer 26

Mass number of an atom is the total number of protons and neutrons in the nucleus of an atom.