3.3 Collisions of Electrons with Atoms

Question 1

What is an ion

Answer 1

A charged atom

Question 2

What is special about ions

Answer 2

The number of electrons is not equal to the number of protons

Question 3

How is an ion formed

Answer 3

When adding or removing electrons from an uncharged atom

Question 4

What happens if electrons are added to an atom

Answer 4

It becomes a negative ion

Question 5

Any process of creating ions is called ______.

Answer 5

Ionisation

Question 6

Alpha, beta and gamma radiation create ions when they pass through ______ and ______ with the atoms of the substance.

Answer 6

Substances

Collide

Question 7

Electrons passing through a ______ tube create ions when they ______ with the atoms of the gas or vapour in the tube.

Answer 7

Fluorescent

Collide

Question 8

How can we measure the energy needed to ionise a gas atom

Answer 8

By making electrons collide at increasing speed with the gas atoms in a sealed tube
The electrons are emitted from heated filament in tube and are attracted to a positive metal plate (anode) at other end of tube

Question 9

What conditions are necessary to measure the energy needed to ionise a gas atom

Answer 9

Gas must be at a sufficiently low pressure otherwise there are too many atoms in tube and electrons cannot reach the anode
Potential difference between anode and filament is increased to increase speed of electrons
Ionisation near anode causes much greater current to pass through ammeter
By measuring pd when current starts to increase, we can calculate ionisation energy of gas atom as this is equal to work done on each electron from filament

Question 10

The work done on each electron from the filament is given by its…

Answer 10

charge e * the tube potential difference V

Question 11

The ionisation energy of a gas atom =

Answer 11

eV

Question 12

What is the electron volt

Answer 12

A unit of energy equal to the work done when an electron is moved through a pd of 1V

Question 13

For a charge q moved through a pd V, the work done =

Answer 13

qV

Question 14

The work done when an electron moved through a potential difference of 1V is equal to…

Answer 14

1.6*10^-19 J

This amount of energy is defined as 1 eV (electron volt)

Question 15

The work done on an electron when it moves through a potential difference of 1000V is…

Answer 15

1000eV

Question 16

The work done on an ion of charge +2e when it moves through a potential difference of 10V is…

Answer 16

20eV

Question 17

What is the process of excitation

Answer 17

The process of gas atoms being able to absorb energy from colliding electrons without being ionised
Happens at certain energies which are characteristic of the atoms of the gas

Question 18

If a ______ electron does not have enough kinetic energy to cause ______, it is deflected by the ______, with no overall loss of kinetic energy.

Answer 18

Colliding
Excitation
Atom

Question 19

What are an atom’s excitation energies

Answer 19

The energy values at which an atom absorbs energy

Question 20

How can we determine the excitation energies of atoms in a gas-filled tube

Answer 20

By increasing the potential difference between the filament and the anode and measuring the pd when the anode current falls

Question 21

When excitation occurs, the ______ ______ makes an electron inside the atom ______ ______ from the nucleus of the atom. The excitation energy is always ______ than the ______ energy of the atom as the atomic electron is not removed completely from the atom when excitation occurs.

Answer 21

Colliding electron
Move away
Less
Ionisation