Atomic Theory & Radioactivity Flashcards
What is an element?
A substance mad from one or more types of atoms
What is an atom?
Smallest particle of matter
What is a compound?
A substance made from two or more different types of atoms
What is a molecule?
A substance made from two or more atoms that are chemically combined. It doesn’t matter if they are the same or different types of atoms but they must all be non-metals.
What is a lattice?
A substance made from two or more atoms that are chemically combined. It doesn’t matter if they are the same or different atoms. Usually they include a metal, except for diamond and graphite.
What is a mixture?
Contains two or more different substances that are not chemically combined. It may be a combination of atoms/molecules/elements/compounds.
What is a pure substance?
Only one type of substance
What are nucleons?
Protons and neutrons
What are protons?
Protons have a positive charge and they are located in the nucleus of an atom.
What are neutrons?
Have no charge and are located in the nucleus of an atom.
What are electrons?
They have a negative charge and are located in the outer shells of an electron. The are much lighter than protons and neutrons.
What does the atomic number of an atom represent?
The number of protons (and therefore electrons) in an atom
What does the atomic mass number represent?
The number of protons plus the number of neutrons
What is an isotope?
Isotopes have the same atomic number but a different mass number indicating a different number of neutrons.
What are ions?
Ions are charged atoms and are made when an atom either accepts or gives away electrons.
What is an anion?
A negatively charged ion
What is a cation?
A positively charged ion
What is the relationship between location in the periodic table and the number of electrons in the outermost shell?
The amount of electrons in the outermost shell corresponds with the group number.
What is the relationship between location in the periodic table and the number of electron shells?
The period in which the atom is located on the periodic table is the same as the amount of shells an atom has.
What are valence electrons?
Electrons in the outermost shell
What are the noble gases?
They are located on the far right side of the periodic table and have a low reactivity due to their valence shell being full.
What is radioactivity?
Is when atoms emits radioactive particles or rays in order to maintain stability in the the nucleus
What causes radiation?
When the nucleus of an atom becomes unstable
How does radiation happen?
When the nucleus is unstable it tries to become stable by losing a small ‘bit’ of
itself. This means that is changes into a different element (called a daughter isotope) and an extra ‘bit’
What are the three types of radiation?
Alpha, beta and gamma
What happens in alpha radiation?
An alpha particle has two protons and two neutrons, giving it a positive charge. When an atom emits alpha radiation, the atoms mass number decreases by 4 and the atomic number decreases by 2. As a result of the loss of two protons the atom becomes a different element
What happens in beta radiation?
A beta particle is the same as an electron except that it is created in the nucleus. Beta emission occurs in elements with more neutrons than protons, so a neutron splits into a proton and an electron. The proton stays and the electron is emitted.
What is gamma radiation?
When a nucleus is in an excited state (usually after it has emitted alpha or beta particles) it may emit one or more photons. Gamma rays do not change the atomic number or mass of the atom but rather move it from a higher energy state to a lower energy state.
What are the two methods of measuring radiation?
Becquerels and half-life
What is the becquerel?
It is a measure of how many atoms break down per second. 1bq is the same as one emission per second.
What is a half-life?
The time it takes for half of a radioactive material sample to decay or break down.
What is a use for alpha radiation?
Alpha radiation is used in smoke alarms to detect smoke. The alpha radiation ionises the air particles inside the smoke dectector. This allows a small electric current to flow. Smoke causes the amount of ionised air particles to drop, setting off the alarm.
What is a use for beta radiation?
Doctors may use radioactive chemicals called tracers for medical imaging. Certain chemicals concentrate in different, damaged or diseased parts of the body. Radiation detectors create a picture of this.
What is a use for gamma radiation?
Gamma radiation is used in the treatment of cancer to kill the cancer cells.
Which is the most damaging form of radiation inside the body?
Alpha is the most dangerous type of radiation to have in your body as it releases lots of energy in a small space.
What is the most dangerous form of radiation externally?
Gamma radiation because it can penetrate the body.
