Particles Flashcards
What are atoms made up of?
Protons, Neutrons and Electrons
What is there inside every atom?
A nucleus
What does the nucleus contain?
Protons and Neutrons
What are protons and neutrons both known as?
Nucleons
What are nucleons?
Protons and neutrons are both known as nucleons
What orbits the nucleus of an atom?
Electrons
Why do we generally use the relative charge and mass of subatomic particles?
Because their charges and masses are so tiny that its often easier to talk about their relative charges and masses
What is the relative charge of a proton?
+1
What is the relative charge of a neutron?
0
What is the relative charge of an electron?
-1
What is the relative mass of a proton?
1
What is the relative mass of a neutron?
1
What is the relative mass of an electron?
0.0005
What is the proton number?
The proton number is the number of protons in the nucleus
What is the proton number sometimes called and what is its symbol?
The proton number is sometimes called the atomic number and has the symbol Z.
Z is just the number of protons in the nucleus
What is the relationship between the proton number and the definition of an element?
Its the proton number that defines an element, no two elements will have the same number of protons
In a neutral atom what is the relationship between the number of electrons and protons?
In a neutral atom the number of electrons equals the number of protons.
What does an element’s reactions and chemical behaviour depend on?
The number of electrons
What is an ion?
An ion is a particle with a different number of electrons to protons
What is the nucleon number?
The nucleon number is the total number of protons and neutrons
What is the nucleon number also called and what symbol does it have?
The nucleon number is also called the mass number and has the symbol A
What is the number of nucleons in an atom the same as and why?
Since each proton or neutron has a relative mass of 1 and the electrons weigh virtually nothing the number of nucleons is the same as the atom’s relative mass
What does the nuclide notation of an element do?
Summarise information about its atomic structure
Is the nucleon number the top or bottom number on an elements nuclide notation?
Top
Is the proton number the top or bottom number on an elements nuclide notation?
Bottom
What are isotopes?
Isotopes are atoms with the same number of protons but different numbers of neutrons
What are isotopes in terms of nuclide notation?
Isotopes have the same proton number but different nucleon numbers
What is the relationship between changing the number of neutrons and an atom’s chemical properties?
Changing the number of neutrons doesn’t affect the atoms chemical properties
What does the number of neutrons affect?
The stability of the nucleus
What does the stability of the nucleus depend on?
The number of neutrons
What may unstable nuclei be and what may they do over time?
Unstable nuclei may be radioactive and decay over time into different nuclei that are more stable
What can radioactive isotopes be used for?
To find out how old things are
How can radioactive isotopes be used to find out how old things are?
1- All living things contain the same percentage of radioactive carbon-14 taken in from the atmosphere
2- After they die the amount of carbon-14 inside them decreases over time as it decays to stable elements
3- Scientists can calculate the approximate age of archaeological finds made from dead organic matter by using isotopic data (amount of each isotope present) to find the percentage of radioactive carbon-14 that’s left in the object
What is the specific charge of a particle?
The specific charge of a particle is the ratio of its charge to its mass
What are the units of specific charge?
Coulombs per kilogram (C/Kg)
What is the formula used to calculate specific charge?
Specific charge = Charge / Mass
What is a fundamental particle?
A fundamental particle is one that you can’t break up into anything smaller
When calculating the specific charge of an ion that has lost an electron what do you need to consider?
The overall charge of the ion which is done by deducing how many protons and electrons there are now present in the ion
What binds nucleons together?
The strong nuclear force
What are the two forces acting on the protons and neutrons in a nucleus?
- Electrostatic forces from the proton’s electric charges
- Gravitational forces due to the masses of the particles
What is the strong nuclear force?
The strong nuclear force is an attractive force that holds the protons and neutrons in the nucleus together therefore holding the nucleus together
Explain why the strong nuclear force exists
The repulsion from the electrostatic force is much bigger than the gravitational attraction between nucleons. If these were the only forces acting in the nucleus the nucleons would fly apart so there must be another attractive force that holds the nucleus together called the strong nuclear force
In order to hold the nucleus together what must the strong nuclear force be in relation to the electrostatic force?
To hold the nucleus together it must be an attractive force that’s stronger than the electrostatic force
What is the general size of the range of the strong nuclear force?
Experiments have shown that the strong nuclear force has a very short range. It can only hold nucleons together when they are separated by up to a few femtometres - the size of a nucleus
What is the relationship between the strength of the strong nuclear force and its range?
The strength of the strong nuclear force quickly falls beyond its range (a few femtometers)
What is the relationship between the strong nuclear force and all nucelons?
Experiments show that the strong nuclear force works equally between all nucleons. This means that the size of the force is the same whether its proton-proton, neutron-neutron or proton-neutron
What can be said about the strong nuclear force at very small separations of nucleons?
At very small separations of nucleons the strong nuclear force must be repulsive or it would crush the nucleus to a point
What does the size of the strong nuclear force depend on?
Nucleon separation
At what distance of nucleon separation is the strong nuclear force repulsive?
Less than 0.5 femtometres
As nucleon separation increases past 0.5fm what happens to the strong nuclear force?
The strong nuclear force becomes attractive. It reaches a maximum attractive value and then falls rapidly towards zero after 3fm
At what distance of nucleon separation is the strong nuclear force attractive?
Between 0.5fm and 3fm
What is the general size of the range of the electrostatic repulsive force?
The electrostatic repulsive force extends over a much larger range than the strong nuclear force (indefinitely)
Where does alpha emission happen?
Alpha emission only happens in very big nuclei like uranium and radium
Why does alpha emission happen in very big nuclei?
Alpha emission only happens in very big nuclei as the nuclei of these atoms are just too massive for the strong nuclear force to keep them stable
What is the effect on the nuclide notation of an element when an alpha particle is released?
The proton number decreases by two and the nucleon number decreases by four
What is the range of alpha particles and how can this be observed?
- Alpha particles have a very short range, only a few cm in air.
- This can be seen by observing the tracks left by alpha particles in a cloud chamber. You could also use a Geiger counter ( a device that measures the amount of ionising radiation). Bring it up close to the alpha source, then move it away slowly and observe how the count rate drops
Where does beta minus decay happen?
Beta minus decay happens in neutron rich nuclei which are isotopes that are unstable due to having too many more neutrons than protons in their nucleus
What is beta minus decay?
Beta minus decay is the emission of an electron from the nucleus along with an antineutrino
What happens when a nucleus ejects a beta particle?
When a nucleus ejects a beta particle one of the neutrons in the nucleus is changed into a proton
What is the effect on the nuclide notation of an element when a beta particle is ejected from a nucleus?
The proton number increases by one and the nucleon number stays the same
What is the relationship between the range of an alpha particle and a beta particle?
Beta particles have a much greater range than alpha particles
In beta decay as well as a beta particle what do you also get?
In beta decay as well as a beta particle you also get a tiny neutral particle called an antineutrino released. This antineutrino carries away some energy and momentum
Why were neutrinos first hypothesised?
Neutrinos were first hypothesised due to observations of beta decay
Explain how observations of beta decay led to the hypothesis of the neutrino
1- Scientists originally thought that the only particle emitted from the nucleus during beta decay was an electron.
2- However, observations showed that the energy of the particles after the beta decay was less than it was before which didn’t fit with the principle of conservation of energy
3- In 1930 Wolfgang Pauli suggested another particle was being emitted too and it carried away the missing energy. This particle had to be neutral or charge wouldn’t be conserved in beta decay and had to have zero or almost zero mass as it had never been detected
4- Other discoveries led to Pauli’s theory becoming accepted and the particle was named the neutrino
What are photons?
Photons are packets of electromagnetic radiation
What is the electromagnetic spectrum?
The electromagnetic spectrum is a continuous spectrum of all the possible frequencies of electromagnetic radiation
What is the electromagnetic spectrum in order of frequency from lowest to highest and wavelength from highest to lowest?
1- Radio waves
2- Micro waves
3- Infra red
4- Visible light
5- Ultraviolet
6- X-rays
7- Gamma rays
What equation links frequency and wavelength?
- f=c/λ
c = 3.00*10^8
What does electromagnetic radiation exist as?
Electromagnetic radiation exists as photons of energy
What does the energy of a photon depend on?
The energy of a photon depends on the frequency of the radiation
What is the formula used to calculate the energy of a photon?
E=hf=hc/λ
What does every particle have?
Every particle has an antiparticle
What are the properties of a particle’s antiparticle?
Each particle has a matching antiparticle with the same mass and rest energy but with opposite charge
What is the antiparticle of a proton
An antiproton
What is the antiparticle of a neutron?
An antineutron
What is the antiparticle of an electron?
A positron
What is the antiparticle of a neutrino?
An antineutrino
How do you convert MeV to joules?
- Multiply by 10^6 to get eV
- Multiply by 1.6*10^-19 to get Joules
What is the relationship between matter and antimatter and energy?
You can create matter and antimatter from energy
What is the rest energy of a particle?
The rest energy of a particle is just the energy equivalent of the particle’s mass measured in MeV
What happens when energy is converted into mass?
When energy is converted into mass you get equal amounts of matter and antimatter