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Chapter 22(radioactivity) - Coggle Diagram
Chapter 22(radioactivity)
An atom consits of a positively charged nucleus and negatively charged electrons moving around the nucleus.Strong attractive forces between the positively charged nucleus and negatively chared electrons hold the electrons to the atom
Protons and neutrons are found in the centre of the atom.They form the nucleus.The lithium atom is made up of 3 protons and 4 neutrons.The mass of the nucleus is almost the mass of the atom(cuz electrons are about 1/1840grams or 9.109 x 10 to the power of -31)
Protons, neutrons and electrons are called subatomic particles.The amount of charge carried by each proton is the same as en electron
Coloumb is the standard SI unit of electrical charge which represents the number of protons and electrons which is approximately 6.24 x 10 to the power of 18 in just 1 Ampere
Formula for coloumb is:C=Ampere x seconds
The proton number is the number of protons in an atom
The symbol Z is used to represent the proton number of an element.The proton number is also known as the atomic number
In a neutral atom, the total positive charge equals to he total negative charge.Therefore, in a neutral atom, the number of protons is the same as the number of electrons
Nucleon (mass) number A
Protons and neutrons are called nucleons
The nucleon number is the total number of neutrons and protons in the nucleus of an atom
The symbol A is used to represent the nucleon number of an element
The nucleon number is also known as the mass number.
This is because the mass of an atom depends on the mass of nucleons in the nucleus of the atom.The mass of an electron is too small and can be neglected
Number of neutrons
Nucleon number A - proton number Z in a nucleus
In nuclear physics and nuclear chemistry, the various species of atoms whose nuclei contain a particular number of protons and neutrons are called nuclides
The nucleus of an atom can be represented by the nuclide notation
Isotopes
Usually they are of the same element and have different nucleon number but they retain the same number of protons
Isotopes are atoms that have the same element but different nucleon numbers.Many elements have isotopes.Isotopes of the same element have identical chemical properties
Nuclear decay is a random process by which an unstable atomic nucleus loses its energy by emission of electromagnetic radiation or particles
nuclear decay is also known as radioactive decay or radioactivity.A material containing unstable nuclei is considered radioactive
The instability of the atomic nuclei is because the nuclear forces within the nuclei are not enough to bind the nucleons together
Radiation emitted by a radioactive nucleus is spontaneous and random in direction.The direction of the emissions and the time between emissions cannot be predicted
The weakening of nuclear forces could be due to an excess of protons in the nucleus as the protons exert repulsive forces against 1 another(just like norht pole and north pole repelling away)
For the atom to become stable again, the atoms loses energy by emitting radiation or nucleons
There are 3 types of nuclear emission
Alpha rays, beta rays and gamma rays
Gamma rays can easily pass through material such as thick lead, aluminium and paper and lots of other materials
Beta ray can only pass through air and thin pieces of materials like paper
Alpha rays can only travel a few cm in the air cuz of their charge and large mass, they are easily absorbed by materials
Even though alpha rays usually get absorbed, it can penetrate the human skin by 40 micrometres which is a few cells deep
Ionisation
Refers to the ability to eject electrons from atoms to form ions.Since the atoms lose electrons, the number of protons is greater than the number of electrons.Thus ions carry a charge
nuclear emission of alpha-particles
An a-particle consists of 2 protons and 2 neutrons tightly bound together.It is identical to a helium nucleus
It has the highest relative ionising effect
Its relative penetrating ability is the least and can be easily absorbed by a piece of paper or human skin
A Beta-particle is a fast-moving electron ejected from a radioactive nucleus
Its relative ionising effect is medium
Its relative penetrating effect is medium and can be absorbed by aluminium that is a few millimetres thick