Atomic structure Flashcards
The structure of an atom
Give two ways that an atom’s electron arrangement can be changed.
- Absorbing electromagnetic radiation
- Emitting electromanetic radiation
The structure of an atom
Explain how an atom’s electron arrangement changes when it absorbs EM radiation
- Electrons move further away from the nucleus
- The move to a higher energy level
The structure of an atom
Explain how an atom’s electron arrangement changes when it emitts EM radiation
- Electrons move closer to the nucleus
- They move to a lower energy level
Mass number, atomic number and isotopes
What is an isotope?
An atom of the same chemical element, with the same number of protons but a different number of neutrons
The development of the model of the atom
Describe John Dalton’s model of the atom
A solid sphere, that couldn’t be broken down into smaller parts, like a billard ball
The development of the model of the atom
Describe J.J Thomson’s model of the atom
In 1897, J.J Thomson discovered electrons.
His model is a ball of positive charge, with negative electrons embedded throughout it. He called it the plum-pudding model
The development of the model of the atom
Describe Ernest Rutherford’s observations and conclusions of his alpha scattering investigation
In 1909, Ruthford fired a beam of alpha particles through a sheet of gold foil. His observations were:
- most particles went straight through
- some were deflected back
- some defleccted at different angles
He concluded:
- most of the atom is empty space
- the mass is concentrated in the centre
- the nucleus has a positive charge
The development of the model of the atom
Describe the first nuclear model
A positively charged nucleus, surrounded by a cloud of negatively charged electrons
The development of the model of the atom
Describe what Niels Bohr discovered
In 1913, he discovered that electrons orbit the nucleus at specific distances, called energy levels.
The development of the model of the atom
Describe Rutherford’s second adaptation to the nuclear model
In 1919, Rutherford added that the postive charge of the nucleus could be broken down into smaller parts, called protons
The development of the model of the atom
Describe what James Chadwick’s discovered
In 1932, Chadwick discovered the existance of neutrons.
This helped explain the imbalance between the atomic number and the mass number.
This contributed to our understanding of isotopes
Radioactive decay and nuclear radiation
What will an unstable atom do to become stable?
To become stable, the nucleus of the unstable atom will emit mass or energy
Radioactive decay and nuclear radiation
What is radiation?
The mass or energy that they emit is called radiation
Radioactive decay and nuclear radiation
What does radioactive decay mean?
The process of an unstable atom emitting radiation to become stable. It is a random process.
Radioactive decay and nuclear radiation
What is ionising radiation?
The radiation that is emitted from the nucleus is called ionising radiation because it has enough energy to knock electrons off an atom, turning that atom into an ion.
Radioactive decay and nuclear radiation
Describe the properties of alpha particles.
- 2+ charge
- mass of 4
- least penetrating
- most ionising
- shortest range in air (5cm)
- can be stopped by skin, paper and card
Radioactive decay and nuclear radiation
Describe the structure of an alpha particle
2 protons, 2 neutrons
Radioactive decay and nuclear radiation
Describe the properties of beta particles
- -1 charge
- mass of 1/2000
- moderately penetrating
- moderately ionising
- can travel 1m through the air
- can be absorbed by a thin sheet of aluminium (5mm)
Radioactive decay and nuclear radiation
Describe the structure of beta particles
1 fast moving electron
Radioactive decay and nuclear radiation
Describe the proprties of gamma rays
- no charge
- no mass
- most penetrating
- least ionising
- longest range in air (1km)
- can be absorbed by thick lead or thick concrete
Radioactive decay and nuclear radiation
What is gamma radiation an example of?
An EM wave
