4.1 Atoms and isotopes

Question 1

Give an approximation for the radius of an atom

Answer 1

1x10 to the power of -10 meters

Question 2

What are the three subatomic constituents of an atom?

Answer 2

Proton, neutron, electron

Question 3

Where is most of the mass of an atom concentrated?

Answer 3

In the nucleus

Question 4

Approximately what proportion of the total radius of an atom is the radius of the nucleus?

Answer 4

1/10,000

Question 5

Describe the arrangement of protons, neutrons and electrons in an atom

Answer 5

The protons and neutrons are found in the atom’s nucleus. The electrons are found in discrete energy levels around the nucleus.

Question 6

What type of charge does the nucleus of an atom have? Why?

Answer 6

Positive charge - the nucleus contains protons and neutrons. Protons have a positive charge but neutrons have no charge.

Question 7

Give two ways that an atom’s electron arrangement can be changed

Answer 7

● Absorbing electromagnetic radiation

● Emitting electromagnetic radiation

Question 8

Explain how an atom’s electron arrangement changes when it absorbs electromagnetic radiation

Answer 8

Electrons move further away from the nucleus to a higher energy level.

Question 9

Explain how an atom’s electron arrangement changes when it emits electromagnetic radiation.

Answer 9

Electrons move closer to the nucleus to a lower energy level.

Question 10

How does the ratio of electrons to protons in an atom result in an atom having no overall charge?

Answer 10

The number of protons is equal to the number of electrons. Protons and electrons have equal and opposite charges so the charges cancel.

Question 11

What do all forms of the same element have in common?

Answer 11

They all have the same number of protons

Question 12

What is the name given to the number of protons in an atom?

Answer 12

Atomic number

Question 13

What is an atom’s mass number?

Answer 13

The total number of protons and neutrons in the atom

Question 14

What is an isotope of an atom?

Answer 14

An atom of an element that has a different number of neutrons, but the same number of protons.

Question 15

How do atoms turn into positive ions?

Answer 15

They lose one or more of their outer electrons. Electrons are negatively charged, so the resulting charge of the atom is positive.

Question 16

What may lead to a scientific model being changed or replaced?

Answer 16

The discovery of new experimental evidence which doesn’t agree with the existing theory.

Question 17

How did the plum pudding model describe the atom?

Answer 17

A ball of positive charge, with negatively charged electrons distributed evenly throughout it.

Question 18

Prior to the discovery of the electron, what was believed about the atom?

Answer 18

The atom was believed to be indivisible

Question 19

Which experiment led to the plum pudding model being discarded?

Answer 19

Rutherford’s alpha scattering experiment

Question 20

What is the name given to the currently accepted model of the atom?

Answer 20

The planetary model / Bohr nuclear model

Question 21

State the conclusions of the alpha scattering experiment

Answer 21

Most of the massive in the atom is concentrated at the center in the nucleus. The nucleus is positively charged.

Question 22

What reinforces a scientific theory?

Answer 22

When experimental results agree with the hypothesised theoretical calculations and theories.

Question 23

What did James Chadwick’s experiments on the atom prove?

Answer 23

The existence of neutrons