Physics Atomic Structure July 2018 Flashcards
What are found in atoms?
Protons, neutrons and electrons
What are the charges of protons, neutrons and electrons?
Proton = +1 Neutron = 0 Electron = -1
What are the masses of protons, neutrons and electrons?
Proton = 1 Neutron = 1 Electron = 0 (1/1840)
What is a proton?
A positively charged particle which is found in the nucleus of an atom.
What is a neutron?
A neutral particle found inside the nucleus of an atom.
What is an electron?
A negatively charged particle that orbits the nucleus of an atom on energy levels or shells.
What is an ion?
An ion is an atom that has gained or lost 1 or more electrons to gain a full outer shell.
What is the atomic number?
Number of protons. The bottom number.
What is the mass number?
Number of protons + Neutrons. The top number.
What is an isotope?
An atom that has gained or lost 1 or more neutrons.
What is an alpha particle?
A particle that is formed by 2 protons and 2 neutrons (a helium nucleus).
What is a beta particle?
A fast moving electron.
What is a gamma ray?
An electromagnetic wave.
What is the Geiger-Müller tube?
A device which detects ionising radiation. An electronic counter can record the number of particles entering the tube.
What is ionisation?
When alpha particles bounce off of other particles, the attractive force between the + charge of the particle and - charge of the electron pulls the electron out of the atom. This is called ionisation due to the original atom losing an electron.
What are the ionising powers of alpha and beta particles and gamma rays?
Alpha- Very strong
Beta - Medium
Gamma - Weak
What are the penetrating powers of alpha and beta particles and gamma rays?
Alpha- Stopped by paper
Beta - Stopped by aluminium
Gamma - Stopped by thick lead (5cm thick)
What is background count?
The average count rate which a Geiger-Müller tube records over a period of time.
What is background radiation?
Comes from natural man-made sources in our environment.
What is half-life?
The time taken for the number of a nuclei in a radioactive isotope to halve. (in one half-live, the activity or count rate of a radioactive sample also halves).
What is a becquerel?
An emmision of 1 particle/second (1/Bq)
What is nuclear fission?
The process of which a large unstable radioactive nuclei are hit by a neutron. They combine to make an even more unstable nucleus that is so unstable that it splits into 2 new nuclei as well as emitting 3 neutrons.
What is nuclear fusion?
The process of joining small nuclei to form large ones.
How was the nucleus of an atom discovered?
Plum pudding model –> Nuclear model
An alpha stream of particles was fired into a thin sheet of gold foil. Some of the particles were reflected signifying that mass is concentrated in the centre around a structure e.g. the nucleus. (Most particles went straight through).
