1.2 Basic Ideas about atoms (radioactivity) Flashcards
What are atoms made up of?
Protons
Neutrons
Electrons
What is the nucleus made up of?
Protons and neutrons.
Where are electrons found?
Surrounding the nucleus on the peripheral of the atom.
What is the atomic number?
The number of protons in the nucleus of an atom.
What is the mass number?
The number of protons + the number of neutrons in the nucleus of an atom.
What is an isotope?
Atoms having the same number of protons but different number of neutrons.
What is an ion?
A particle where the number of electrons does not equal the number of protons.
What are three things to remember about an atom?
The atomic number = number of protons
The number of protons = the number of electrons
The number of neutrons = the mass number - the atomic number
On the periodic table, where is the mass number and the atomic number seen?
The mass number is seen above the symbol and the atomic number is seen below the symbol
What are cations and anions?
Cation is a positive ion and an anion is a negative ion.
What are the three types of radiation?
Alpha, beta and gamma.
How do the radiation types get defected in an electric field?
Discuss alpha particles:
Alpha particles consist of two protons and two neutrons and are therefore helium nuclei. They are the least penetrating of the three types of radiation and are stopped by a thin sheet of paper or even a few centimetres of air. Alpha particles are the most ionising of the three as they are large, slow moving and carry two positive charges.
Discuss Beta particles:
Beta particles consist of streams of high-energy electrons and are more penetrating. They can travel through up to 1m of air but are stopped by 5mm thick sheet of aluminium.
Discuss gamma rays:
Gamma rays are high-energy electromagnetic waves and are the most penetrating of the three radiations. They can pass through several centimetres of lead or more than a metre of concrete. But gamma rays are the least ionising due to being the most penetrating.
What is the order of ionisation in the three radiation types and give a reason why:
Ionisation involves a transfer of energy from the radiation passing through the matter to the matter itself. Alpha is the most ionising as it’s the biggest and slowest moving (least penetrating), therefore gamma rays are the least ionising as they are the quickest and most penetrating.
What happens when an element emits an alpha particle?
Its mass number decreases by 4 and its atomic number decreases by 2.
The product is found two places to the left in the periodic table.
What happens when an element emits a beta particle?
Its mass number is unchanged and its atomic number increases by 1.
The product is one place to the right in the periodic table.
What is inverse beta decay?
This is known as electron capture. I. The process of electron capture, one of the orbital electron last is captured by a proton in the nucleus, forming a neutron ( and emitting an electron neutrino)
The product is one place to the left in the periodic table.
What is another type of beta decay?
Positron emission or B+ decay. In this process a proton is converted into a neutron while releasing a positron ( and an electron neutrino). The positron is a type of beta particle.
The product is one place to the left in the periodic table.
What does half life mean?
Half life is the time taken for half of the atoms in a radioisotope to decay or the time taken for the radioactivity of a radioisotope to fall to half of its initial value.
Give a summary of what half life looks like in radioactive decay:
Similar to a knockout tournament where half the competitors will be removed each round, but the number of competitors leaving each round does decrease. With radiative decay, the amount of time it takes for half the number of radioactive atoms to decay remains the same, but the amount of radioactive atoms decaying does reduce each tim. E.G if N= number of atoms then N/2, N/4, N/8 all equal the same amount of time taken.
Why is it a greater concern if the half life is longer?
The greater the half life of an atom the greater the concern as the radioactivity of the isotope exists for a longer time .
