Physics Flashcards
What is most of an atom?
empty space
Where is all of an atoms mass concentrated?
In the nucleus
What did Rutherfords Experiment involve?
It involved firing positively charged alpha particles at a thin peice of gold foil
How many alpha particles bounced back in Rutherfords Experiment?
1 in 800
What did the Rutherford Scattering Experiment conclude?
That an atom is made up of a small, positively charged nucleus surrounding by electrons orbiting it.
Who made the plum pudding model?
J.J. Thomson’s
What is the plum pudding model?
negatively charged electrons surrounded by a sea of positive charge
What did Niels Bohr discover?
He adapted to the nuclear model by suggesting that electrons orbit the nucleus at specific distances, called energy levels.
What did James Chadwick discover?
the existence of neutrons within the nucleus
How do you find the atomic mass number?
protons + neutrons
How do you find the amount of protons and electrons ?
the atomic number = the protons and electrons
What is an Isotope?
An atom with the same number of protons and a different number of neutrons.
Why are Isotopes identical in their chemical reaction?
because they have the same number of protons and electrons
What is Radioactivity?
Some Isotopes are radioactive meaning they are unstable as they have too many neutrons.
What is Ionisation?
When radiation knocks electrons off of atoms
Why is Ionisation dangerous?
It is dangerous as it can harm DNA.
What is Radioactive Decay?
Is when a nucleus of an atom emits alpha, beta or gamma radiation
What are the 3 types of Radioactive Decay?
Alpha Decay, Gamma Decay, Beta Decay
What is a alpha particle?
2 protons and 2 neutrons. the same as a helium nucleus
What is a beta particle?
Is a high energy electron emmited from the nucleus when a neutron turns into a proton.
What is gamma radiation?
Is a high energy electromagnetic radiation wave, not a type of particle
What is an Alpha Particles charge and mass?
Charge = +2 Mass = 4
What is a Beta Particles charge and mass?
Charge = -1 Mass = 0
What is the charge and mass of Gamma Radiation?
Has no mass or charge
What is an alpha particle stopped by?
paper
What is a beta particle stopped by?
5mm of aluminum
What stops gamma radiation?
5cm of lead
How penetrating and ionising is an alpha particle?
How Penetrating = Low
How Ionising = High
How penetrating and ionising is a beta particle?
How Penetrating = Medium How Ionising = Medium
How penetrating and ionising is gamma radiation?
How Penetrating = High
How Ionising = Low
What is an Alpha Decays Equation?
The helium stays the same and the:
Mass Number decreases by 4
Atomic Number decreases by 2
What is a Beta Decays Equation?
The “e”(electron) stays the same:
Mass Number is unchanged
Atomic Number increases by 1
Why is the atomic mass and number unchanged in Gamma Equation?
There is no change to make up of the nucleus and so a new element is NOT formed
What is Neutron Emission?
It is another way of stabilising the nuclei but by emitting a neutron
What is Neutron Emission equation?
The “n” (neutron) stays the same:
The atomic mass decreases by 1
The atomic number is unchanged
What is Activity? (count rate)
Number of decays per second
What is a geiger counter?
The device used to measure activity
What is a Half-Life?
Average time taken for activity or number of radioactive nuclei to halve
A 1000g radioactive sample has a half life of 2 years. How much will still be radioactive after…
1. 2 years?
2. 4 years?
3. 10 years?
- 500g
- 250g
- 31.25g
What is Net Decline?
Is the ratio of atoms which are still radioactive which can be written in fractions.
What is Background Radiation?
Background radiation is the low-level radiation we are exposed to every day (e.g ground,air,food,drink)
3 ways to reduce exposure to Radiation?
- wearing protective clothing
- keeping distance from sources (tongs)
- storing sources in lead lined containers
What is Radiation Dose?
measures possible harm radiation could do to the body in sieverts(sv)
Why is Radiation so dangerous?
because it can cause ionisation which can harm DNA
What is Irradiation?
is when a radioactive material outside the body fires alpha, beta or gamma particles at a living thing
How dangerous is an alpha particle in Irradiation and Contamination?
In Irradiation it is not dangerous as it is blocked by the skin.
In Contamination it is very dangerous as it is highly ionising