🧱
Matter and radiation
Tags Done
Last edited time @December 15, 2023 9:22 PM
Inside the atom
The structure of an atom
Every atom contain protons and neutrons. These form a positively charged nucleus. Because of this they are commonly
referred to as nucleons.
Due to the nucleus being positively charged, the electrons are held in place. This is from the electrostatic attraction from the
positive nucleus and the negative electrons. This is shown by the diagram below:
Charge / C Charge relative to proton Mass / kg Massive relative to proton
proton +1.60x10^-19 1 1.67x10^-27 1
neutron 0 0 1.67x10^-27 1
electron -1.60x10^-19 -1 9.11x10^-31 0.0005
All atoms are uncharged, this is because they have the same number of protons and neutrons and hence, their charges cancel
out.
Isotopes
An isotope is an atom with the same number of protons but a different number of neutrons.
The proton number (atomic number) is the number of protons within the atom. This is represented by Z , and is the same
for every atom of the same element.
The total number of protons and neutrons in an atom is called the nucleon number. This is represented as Aand is
sometimes called the mass number.
Each type of nucleus is called a nuclide and is unique to that element. So a carbon nucleus will always have 6 protons.
All of these conventions combine together to give element notation which is described below.
AX
Z
Where X = chemical symbol, A = mass number, Z = proton number
Specific charge
The specific charge of a particle can also be called its charge to mass ratio. This is because the way to calculate the specific
Q
charge of a particle is given by the equation E = M . Below is the equation in an expanded form.
Matter and radiation 1
, charge on particle [C]
specific charge [Ckg−1 ] =
mass of particle [kg]
The largest specific charge is that of the electron, with a charge of 1.76 ∗ 1011 Ckg−1 . When calculating the specific charge
of a nucleus, you must also consider the number of protons and neutrons within the nucleus. This can be done as follows:
Qt Qp ∗ np
E= =
Mp + Mn
Mt
where Qp = charge of a proton and np = number of protons within the nucleus. And also Mp is the mass of a proton * number
of protons and Mn = mass of a neutron * number of neutrons.
This concepts can be applied to larger structures such as atoms where electron charges must be considered for Qand
electrons masses must also be considered.
Stable and Unstable Nuclei
The strong nuclear force
This is the force that holds the protons and neutrons together in a stable nucleus. This force is stronger than the electrostatic
repulsion between the protons and neutrons.
Its range is no more than about 3-4 femtometres (fm). Where 1fm = 10−15 m. This range is similar to the diameter of a
small nucleus.
The electrostatic force has infinite range. The strength of this force does decrease with range.
The force stops being attractive at around 0.5 fm. At separations smaller than this, the strong nuclear force is a repulsive
force that acts to stop protons and neutrons from crashing into each other.
This can be explained by the diagram below:
The pion is the exchange particle for the strong interaction.
Radioactive decay
There are 3 types of radiation that are emitted from naturally radioactive isotopes. These are Alpha, Beta and gamma radiation.
Alpha Radiation
Alpha radiation is when an atom emits alpha particles. These consist of 2 protons and 2 neutrons. This is can be written as 42 α.
Once an alpha particle has been emitted the atom than becomes element Y . Alpha decay happens as shown below:
AX → A−4 Y + 42 α
Z
Z−2
Beta Radiation
Beta radiation is the emission of fast-moving electrons.
A beta particle can be written as −10 β or as β − .
They are emitted when a neutron in the nucleus changes into a proton. When this change occurs a beta particle is created
ˉ) is also emitted.
and emitted instantly. An antineutrino (symbol ν
Matter and radiation 2
Matter and radiation
Tags Done
Last edited time @December 15, 2023 9:22 PM
Inside the atom
The structure of an atom
Every atom contain protons and neutrons. These form a positively charged nucleus. Because of this they are commonly
referred to as nucleons.
Due to the nucleus being positively charged, the electrons are held in place. This is from the electrostatic attraction from the
positive nucleus and the negative electrons. This is shown by the diagram below:
Charge / C Charge relative to proton Mass / kg Massive relative to proton
proton +1.60x10^-19 1 1.67x10^-27 1
neutron 0 0 1.67x10^-27 1
electron -1.60x10^-19 -1 9.11x10^-31 0.0005
All atoms are uncharged, this is because they have the same number of protons and neutrons and hence, their charges cancel
out.
Isotopes
An isotope is an atom with the same number of protons but a different number of neutrons.
The proton number (atomic number) is the number of protons within the atom. This is represented by Z , and is the same
for every atom of the same element.
The total number of protons and neutrons in an atom is called the nucleon number. This is represented as Aand is
sometimes called the mass number.
Each type of nucleus is called a nuclide and is unique to that element. So a carbon nucleus will always have 6 protons.
All of these conventions combine together to give element notation which is described below.
AX
Z
Where X = chemical symbol, A = mass number, Z = proton number
Specific charge
The specific charge of a particle can also be called its charge to mass ratio. This is because the way to calculate the specific
Q
charge of a particle is given by the equation E = M . Below is the equation in an expanded form.
Matter and radiation 1
, charge on particle [C]
specific charge [Ckg−1 ] =
mass of particle [kg]
The largest specific charge is that of the electron, with a charge of 1.76 ∗ 1011 Ckg−1 . When calculating the specific charge
of a nucleus, you must also consider the number of protons and neutrons within the nucleus. This can be done as follows:
Qt Qp ∗ np
E= =
Mp + Mn
Mt
where Qp = charge of a proton and np = number of protons within the nucleus. And also Mp is the mass of a proton * number
of protons and Mn = mass of a neutron * number of neutrons.
This concepts can be applied to larger structures such as atoms where electron charges must be considered for Qand
electrons masses must also be considered.
Stable and Unstable Nuclei
The strong nuclear force
This is the force that holds the protons and neutrons together in a stable nucleus. This force is stronger than the electrostatic
repulsion between the protons and neutrons.
Its range is no more than about 3-4 femtometres (fm). Where 1fm = 10−15 m. This range is similar to the diameter of a
small nucleus.
The electrostatic force has infinite range. The strength of this force does decrease with range.
The force stops being attractive at around 0.5 fm. At separations smaller than this, the strong nuclear force is a repulsive
force that acts to stop protons and neutrons from crashing into each other.
This can be explained by the diagram below:
The pion is the exchange particle for the strong interaction.
Radioactive decay
There are 3 types of radiation that are emitted from naturally radioactive isotopes. These are Alpha, Beta and gamma radiation.
Alpha Radiation
Alpha radiation is when an atom emits alpha particles. These consist of 2 protons and 2 neutrons. This is can be written as 42 α.
Once an alpha particle has been emitted the atom than becomes element Y . Alpha decay happens as shown below:
AX → A−4 Y + 42 α
Z
Z−2
Beta Radiation
Beta radiation is the emission of fast-moving electrons.
A beta particle can be written as −10 β or as β − .
They are emitted when a neutron in the nucleus changes into a proton. When this change occurs a beta particle is created
ˉ) is also emitted.
and emitted instantly. An antineutrino (symbol ν
Matter and radiation 2
