3.3 Collisions Of Electrons With Atoms *Diagrams

Question 1

What is an ion

Answer 1

A charged atom

Question 2

How is an ion formed

Answer 2

By adding or removing electrons from an uncharged atom

Question 3

What does adding electrons to an atom make

Answer 3

A negative ion

Question 4

What does removing electrons from an atom make

Answer 4

A positive ion

Question 5

What is the process of creating ions called

Answer 5

Ionisation

Question 6

What do alpha beta and gamma radiation create when they passed through substances and collide with the atoms of the substance

Answer 6

Ions

Question 7

What do electrons passing through a fluorescent tube create when they collide with the atoms of gas or vapour in the tube

Answer 7

Ions

Question 8

What is the electron volt

Answer 8

Are units of energy equal to the work done when an electron is move through a potential difference of one volt

Question 9

What is the potential difference of 1 V

Answer 9

1.6x10^-19

Question 10

How can we show that gas atoms can absorb energy from colliding electrons without being ionised

Answer 10

Using gasfield tubes with a metal grid between the filament on the anode

Question 11

What is excitation

Answer 11

When gas atoms can absorb energy from colliding electrons without being ionise

Question 12

When does excitation happen

Answer 12

At certain energy which are characteristics of the atoms of the gas

Question 13

What happens if a colliding electron loses all its kinetic energy when it causes excitation

Answer 13

The current due to the flow of electrons through the gas is reduced.

Question 14

What happens if the colliding electron does not have enough kinetic energy to cause excitation

Answer 14

It is deflected by the atom with no overall loss of kinetic energy

Question 15

What are excitation energies

Answer 15

The energy values of which an atom absorbs energy

Question 16

How can we determine excitation energies of atoms

Answer 16

In gas filled tube

by increasing the potential difference between the filament in the anode and measuring the potential difference when the anode current falls

Question 17

What happens to the electrons in excitation

Answer 17

The colliding electron makes an electron inside the atom move up from an inner to an outer shell

Question 18

Why is energy needed for excitation

Answer 18

Because the atomic electron moves away from the nucleus of the atom

Question 19

Why is excitation energy always less than ionisation energy

Answer 19

Because the atomic electron is not removed completely from the atom when excitation occurs

Question 20

Why does the gas need to be at a sufficiently low pressure when measuring ionisation energy

Answer 20

Otherwise there will be too many atoms in the tube and the electrons can’t reach the anode

Question 21

What happens to the pd when measuring ionisation energy

Answer 21

The pd between the anode and the filament is increased so as to increase the speed of electrons

Question 22

Why does the ammeter record a very small current

Answer 22

Due to electrons from the filament reaching the anode

Question 23

What does no ionisation occur until

Answer 23

Electrons from the filament reach a certain speed

At this speed each electron arrives near the anode with just enough kinetic energy to ionise a gas atom by knocking an electron out of the atom

Question 24

What does ionisation near the anode cause

Answer 24

A much greater current to pass through the ammeter

Question 25

How can we calculate the ionisation energy of a gas atom

Answer 25

By measuring the pd (V) between the filament and the anode when the current starts to increase

Ionisation energy of gas is equal to work done (W) on each election form the filament (and work done is transformed into kinetic energy)

Work done on each electron = charge of electron x tube of potential difference