3.3- COLLISIONS OF ELECTRONS WITH ATOMS Flashcards
What is an ion?
a charged atom
In an ion what is the number of electrons and protons like?
number of electrons is not equal to the number of protons
How is an ion formed?
from an uncharged atom by adding or removing electrons from the atom
What does adding electrons to an atom make it?
negative ion
What does removing electrons from an atom make it?
positive ion
What is the process of making ions called?
ionisation
Examples of ionisation?(2)
alpha, beta, gamma radiation creates ions when they pass through substances + collide with the atoms of the substance
electrons passing through a fluorescent tube create ions when they collide with the atoms of the gas/vapour in the tube
How can we show that gas atoms can absorb energy from colliding electrons without being ionised?
using gas-filled tubes with a metal grid between the filament and the anode
What is it called when atoms can absorb energy from colliding electrons without being ionised?
excitation
When does excitation happen?
at certain energies, which are characteristics of the atoms of the gas
What happens if a colliding electron loses all its K.E. when it causes excitation?
current due to the flow of electrons through the gas is reduced
What happens if a colliding electron does not have enough K.E. to cause excitation?
deflected by the atom, with no overall loss of K.E.
What is excitation energies?
energy values at which an atom absorbs energy
How can we determine the excitation energies of the atoms in a gas-filled tube?
by increasing the p.d. between the filament and the anode and measuring the p.d. when the anode current falls
What happens to the colliding electrons when excitation occurs?
colliding electron makes an electron inside the atom move from an inner shell to an outer shell
