physics term3

nucleus

nucleus

the central region of an atom which consists of protons and neutrons. It contains the most mass in an atom

proton

subatomic particle, mass is 1 and charge is +1

neutron

subatomic particle, mass is 1 and charge is 0. It isn’t stable and can decay to make an electron or proton

electron

subatomic particle, mass is 0.0005 (effectively 0) and charge is -1

the charge of the nucleus of an atom

it depends on the number of protons in the atom an is unique to particular elements

the charge on nucleus is +1

hydrogen

the charge on nucleus is +79

gold

why nuclei of different elements have different masses

Atoms of an element all contain the same number of protons but can also contain different numbers of neutrons- this changes the mass while not changing the charge.

isotopes

atoms with the same number of protons but a different number of isotopes. They are written in the format ‘c-12’ . the -12 refers to the total number subatomic particles in the nucleus.

deuterium

a hydrogen isotope ( hydrogen-2)

stable atoms

atoms that don’t decay or breakdown

unstable atoms

atoms that decay and emit radiation which can be made up of particles or waves. They are radioactive.

radiation

the emission of energy as electromagnetic waves or as moving subatomic particles, especially high-energy particles which cause ionization. there are 3 types.

alpha radiation

A type of particle radiation which is the nucleus of a helium atom. The symbol is α and the equation symbol is ⁴₂He. It has short range, large mass and high ionising power.

beta radiation

A type of particle radiation which is a fast moving electron. The symbol is β and the equation symbol is ⁰₋₁e. It has a medium range, small mass and medium ionising power

gamma radiation

A type of wave which is an electromagnetic wave. The symbol is γ and there is no equation symbol. Its has no mass, no charge and a long range.

neutron radiation

A type of particle radiation which is a particle in the nucleus. The symbol is n and the equation symbol is ¹₀n

geiger counter

a device that clicks when radiation enters it. Each click is a tiny current produced when radiation ionises atoms of the gas inside the tube.

penetrating power

how much material radiation can pass through. (Highest-lowest) gamma, beta alpha

few sheets of a paper, or skin

it can stop alpha radiation.

few mm of aluminium

it can stop beta radiation

few cm of lead or m of concrete

it can stop gamma radiation mostly (some still can pass through)

ionising radiation

radiation emitted by radioactive materials, it can remove electrons from atoms to create positively charged ions.

alpha decay

a nuclear decay process where an unstable nucleus changes to another element by shooting out a particle composed of two protons and two neutrons. This ejected particle is known as an alpha particle and is simply a helium nucleus.

beta decay

a nuclear decay process where a neutron decays into an electron and is emitted as a beta particle. The number of neutrons goes down by one and the number of protons goes up by one.

gamma decay

it is emitted usually alongside an alpha and beta decay. The atomic number and mass stays the same when this happens

neutron emission

when some nuclei decay they produce nuclei with large numbers of neutrons,

activity/ count rate

radiation emitted per second (measured on a Geiger counter). It is measured in becquerels (Bq)

becquerels (Bq)

A unit of measurement for radiation. One becquerels is one count or wave per second. You can measure lower activities in counts per minute

Half-life

The time it takes for the activity to half. It is also the same as the time for the nuclei of half the atoms to decay. the probability for any 1 nucleus to decay in 1 second is fixed which means decay is random and half life is fixed.

Irradiation

When an object is exposed to radiation. This can be used to sterilise food and medical instruments and chemotherapy

Contamination

When a material has a radioactive substance in it