Radioactivity Flashcards
What is the basic structure of an atom?
An atom consists of a small central nucleus made up of protons and neutrons, surrounded by electrons.
What word describes the nucleus of radioactive elements?
How do they become stable, what happens during this process?
The nuclei of radioactive elements are unstable, they become stable in the process of radioactive decay, they emit radiation and turn into other elements.
What three types of radiation are emitted in the process of radioactive decay?
Alpha radiation, Beta radiation and Gamma radiation.
Why can we not predict when an unstable nucleus will decay?
We cannot predict when an unstable nucleus will decay because it is a random process and is not affected by external conditions.
What is background radiation?
Background radiation is radiation from radioactive substances in the environment, from space, from devices such as x-ray tubes that is around us all the time.
What did scientists think atoms consisted of at one time?
What did this model of an atom become know as?
At one time scientists thought that atoms consisted of spheres of positive charge with electrons stuck into them.
This model of the atom became known as the ‘plum pudding’ model.
What experiment did Rutherford, Marsden and Geiger devise and what did it involve?
Rutherford, Marsden and Geiger devised an alpha particle scattering experiment in which they fired alpha particles at thin gold foil.
What happened to the alpha particles in Rutherford, Marsden and Geiger’s experiment?
Most of the alpha particles passed straight through the foil, meaning that most of the atom is just empty space.
Some of the alpha particles deflected through small angles, this suggests that the nucleus has a positive charge.
A few of the particles rebounded through very large angles, this suggests that the nucleus has a large mass and a very large positive charge.
What is the relative charge and mass of proton, neutrons and electrons?
Protons: Relative Charge = +1 Relative Mass = 1
Neutrons: Relative Charge = 0 Relative Mass = 1
Electrons: Relative Charge = -1 Relative Mass = 0.0005
What happens to the nucleus in alpha decay and what particles are emitted?
The nucleus loses 2 protons and 2 neutrons, which are emitted as an alpha particle.
What happens to the nucleus in beta decay and what particles are emitted?
A neutron in the nucleus changes into a proton and an electron, the electron created in the nucleus is instantly emitted.
Why does an atom have no overall charge?
What happens if an atom gains or loses electrons?
An atom has no overall charge because the number of proton = the number of electrons.
If an atom loses or gains electrons it becomes negatively or positively charged and is called an ion.
What are isotopes?
Atoms of the same element with a different number of neutrons.
What is the atomic number of an atom?
What is the mass number of an atom?
The number of protons.
The number of protons plus neutrons.
How many protons and neutrons does an alpha particle have?
What is the relative mass and charge of an alpha particle?
How is an alpha particle represented? (Think of in head)
An alpha particle consists of two protons and two neutrons.
An alpha particle has a relative mass of 4 and its relative charge is +2.
