Atomic Structure Flashcards
Atoms are very small what is the radius of an atom
1×10^ -10 meters
What is the basic structure of an atom
An atom is a positively charged nucleus with both protons and neutrons surrounded by negatively charged electrons
Where is most of the mass of an atom concentrated in
Most of the mass of an atom is concentrated in the nucleus
How are the electrons arranged from the nucleus
The electrons are arranged at different distances from the nucleus (Different energy levels)
The electron arrangements may change with the absorption of electromagnetic radiation (Move further from the nucleus; a higher energy level)
Or by the emission of electromagnetic radiation (Move closer to the nucleus; a lower energy level)
In an atom the number of electrons is equal to the number of what
Protons in the nucleus
Do atoms have a charge
Atoms have no overall electric charge
The total number of protons and neutrons is called
The mass number
All atoms of a particular element have the same number of protons. What is the number of protons called
Atomic number
What can atoms turn into if they lose one or more outer electron
Atoms turn into positive ions
Define isotope
An atom that has the same number of protons but a different number of neutrons.
Before the discovery of the electron what were atoms thought to be
Atoms were thought to be tiny spears that could not be divided
What did the discovery of the electron lead to
The plum pudding model of the atom
What was the plum pudding model suggested to be
The plum pudding model suggested that the item is a ball of positivity charge with negative electrons embedded in it
What model replace the plumbing pudding model
The nuclear model
The results from the alpha particle experiment led to a conclusion of what
That the mass of an atom is concentrated at the center (nucleus) and the nucleus was charged
What was Niels Bohrs theory 
That’s the electrons orbit the nucleus at a specific distance
What did Letcher experiments lied to about the nucleus
That the positive charge of any nucleus could be subdivided into a whole number of smaller particles each particle having the same amount of positive charge. The name proton was given to these particles.
The experimental work of James Chadwick led to the evidence of what
The evidence to show the existence of neutrons within the nucleus
What does the nucleus give out
The nucleus gives out radiation as it changes to become more stable
this is called radioactive decay
Define activity
Activity is the rate at which a source of unstable nuclei decays
What is activity measured in
Becquerel (Bq)
Define current rate
Count rate is the number of the keys recorded each second of a detector (E.g. Geiger-muller tube)
What is an alpha particle
It consists of 2 neutrons and 2 protons its the same as helium nucleus
What is a beta particle
A high-speed/fast moving electron emitted from the nucleus when a neutron turns into a proton and electron
What is gamma ray
Electromagnetic radiation from the nucleus they have no mass or charge
What are nuclear equations used for
Nuclear equations are used to represent radioactive decay
What is radioactive contamination
Radioactive contamination is the unwanted presence of materials containing radioactive atoms on other materials
What are the hazard for contamination
The hazard from contamination is due to the decay of the contaminating atoms (Ionizing radiation)
The type of radiation emitted affects the level of hazard.
What is Irradiation
Irradiation is the process of exposing an object to nuclear radiation (Alpha, Beta, Gamma, neutrons.)
The irradiated object does not become radioactive.
What is meant by ionising power
When radiation collides with atoms that can cause the atoms to lose electrons and form ions
Alpha particles are what with ionizing power
Alpha particles: very strong ionizing but can be easily stopped by a dead cells on the skin surface.
Very dangerous if alpha is inhaled or swallowed
Better particles are what with ionizing power
Butter particles: quite ionized but can penetrate skin into the Body
Gamma radiation are what with ionizing power
Gamma radiation: weakly ionising but can penetrate (Go through matter) body but likely to pass straight through
Define radioactive decay
Radioactive isotopes release radiation from the nucleus of their atoms
This cannot be predicted. Decay is a random process.
Define half life
Half-life of a radioactive isotope is the time it takes for a number of nuclei of the isotope in a sample to halve
What is the risk of ionizing radiation
It can increase the risk of cancer in humans
How can alpha radiation be shielded from humans
By wearing gloves
How can better and gamma radiation be shielded
It can be reduced using a lead apron
What is meant by peer review
When scientists explore the effects of radiation and is shared with other scientists to be checked
What is the difference between radioactive contamination and irradiation
Radioactive contamination occurs when there is a direct contact with radioactive substances
The radiation occurs when there is an indirect exposure to radioactive substances
