Particles and radiation Flashcards
Explain why an atom has no overall charge
An atom has an equal number of protons and electrons which have equal and opposite charges that cancel out, so since neutrons have no charge anyway the overall charge must be zero
What is meant by the term isotope?
A different form of the same element that has the same number of protons but a different number of neutrons so the same atomic number but different mass number
What is isotopic data?
The relative amounts of different isotopes present in a substance
Give a use of isotopic data
Carbon dating (this is done by calculating the percentage of radioactive C-14 left in an object to calculate its approximate age)
Explain why the nucleon numbers on the periodic table are not whole numbers
Because it represents the average nucleon number of all of the isotopes of that element
Describe how a positive ion is formed
When an atom looses one or more electrons
Describe how a negative ion is formed
When an atom gains one or more electrons
What is meant by specific charge?
The ratio of a particles electric charge to its mass
What is a nucleon?
A particle found in the nucleus (protons and neutrons are nucleons)
Describe the range of the strong nuclear force
It is repulsive at very short ranges between 0 fm and 0.5 fm to prevent the nucleus from collapsing in on itself and then it becomes attractive between 0.5 fm and 3 fm and within this range it reaches a maximum value of attraction and then at around 3 fm the size of attraction rapidly falls to zero and the force no longer has an effect
What is the range of the electromagnetic force?
Infinite
What is the importance of the strong nuclear force?
The electromagnetic force causes the positively charged protons to repel eachother in the nucleus and the gravitational force causes all of the nucleons to attract eachother due to their masses, however, the electromagnetic force of repulsion is much stronger than the gravitational attraction so there must be the strong nuclear force of attraction (that is stronger than the electromagnetic repulsion) to prevent the nucleus flying apart
Why does the graph of neutrons against protons curve upwards as the nucleus gets larger?
As the number of protons in a nucleus increases the electromagnetic force of repulsion gets stronger and so more neutrons are needed to maintain stability because adding more neutrons helps to increase the strong nuclear force without contributing to the electromagnetic repulsion
What is an alpha particle?
A Helium nucleus (He2+) meaning it has 2 protons and 2 neutrons
What happens during alpha decay?
A nucleus emits 2 protons and 2 neutrons (an alpha particle) in order to become more stable, this causes the nucleon number to fall by 4 and the proton number to fall by 2
What is a beta-minus particle?
A high speed, high energy electron
What happens during beta-minus decay?
A neutron in the nucleus turns into a proton and in the process a beta-minus particle and an anti-electron neutrino are emitted
What is a beta-plus particle?
A high speed, high energy positron
What happens during beta-plus decay?
A proton in the nucleus turns into a neutron and in the process a beta-plus particle and an electron neutrino are emitted
What was the problem that arose when observing beta decays and how was this solved?
The energy before the decay was not the same as the energy after the decay which violates the law of energy conservation this meant that another particle must be being emitted during the decay but it just hadn’t been detected yet, until Pauli observed the neutrino being emitted
What can you deduce about the neutrino based on its emission in beta-decay?
It has a very tiny mass as it was difficult to detect and also it must have a neutral charge to ensure charge is conserved
What is a gamma ray?
An electromagnetic wave with a high frequency
What happens during gamma emission?
Excess energy is released from the nucleus as it de-excites
Compare a particle with its corresponding antiparticle
They have the same mass and rest energy but they have an equal but opposite charge to each other