Physics Chapter 15: Atomic Structure and particle physics

PHYSICS DEFINITION:

Unified atomic mass unit: One-twelfth of the mass of a carbon-12 atom.

Electronvolt: 1 electronvolt (1 eV) is the energy transferred when an electron travels through a potential difference of 1 volt.

PHYSICS KEYWORD LIST:

Plum Pudding Model of the atom: Model that pictured the atom as a positive sphere of pudding with small negativity charged plums embedded in it.

Nuclear Model of the atom: Model that pictures the atom having a tiny positively charged nucleus that carries almost all of the atom's mass surrounded by the much smaller, negatively charged electrons.

Nucleus (of an atom): Tiny, but very dense, positively charged centre of an atom.

Nucleon: General term to describe protons and neutrons.

Nucleon number: Total number of neutrons and protons in the nucleus of an atom.

Neutron number: Number of neutrons in the nucleus of an atom.

Proton number: Number of protons in the nucleus of an atom.

Nuclide: Specific combinations of protons and neutrons in a nucleus.

Isotopes: Nuclei of the same element with different numbers of neutrons but the same number of protons.

Ion: Atom that has lost or gained one or more electrons, so that it is electrically charged.

Strong nuclear force: Fundamental force that acts between particles such as protons and neutrons, but which does not affect particles like electrons.

Positron: Antiparticle of the electron. It has same mass as the electron but has a charge +e.

Beta minus decay: Emission of an electron as a neutron decays into a proton.’

Beta plus decay: Emission of a positron as a proton decays into a neutron.

Antimatter: Material made up of antiparticles of the corresponding particles of ordinary matter.

Electron neutrino: Particle that is given of with beta plus decay with virtually no rest mass and no charge. (ν)

Electron antineutrino: Antiparticle that is given off with beta minus decay with virtually no rest mass and no charge. (-ve)

Leptons: Subatomic particles that are not affected by the strong nuclear force and are believed to be fundamental.

Hadrons: Subatomic particles made up of quarks that are affected by the strong nuclear force.

Quarks: Fundamental particles that make up hadrons.

Baryon: Hadron made up of 3 quarks.

Meson: Hadron is made up of a quark and an antiquark.

PHYSICS CHAPTER WISE SUMMARY:

The alpha particle scattering experiment provides evidence for the existence of a small, massive and positively charged nucleus at the centre of the atom.

Most of the mass of an atom is concentrated in its nucleus.

The nucleus consists of protons and neutrons and is surrounded by a cloud of electrons.

The number of protons and neutrons in the nucleus of an atom is called its nucleon number.

The number of protons in the nucleus of an atom is called its proton number (or atomic number).

Isotopes are nuclei of the same element with different numbers of neutrons but the same number of protons.

There are 3 types of ionising radiation produced by radioactive substances: Alpha particles, Beta particles and Gamma rays.

In radioactive decay, the following quantities are conserved: proton number, nucleon number and ass energy.

The most strongly ionising and hence the least penetrating is Alpha radiation. The least strongly ionising is Gamma-ray radiation.

Because of their different charges, masses and speeds, the different types of radiation can be identified by the effect of an electric or magnetic field.

Antimatter is material made up of antiparticles of the corresponding particles of ordinary matter.. All particles have an antiparticle, which has the same mass as the particle but the opposite charge.

Quarks are particles that makeup hadrons. There are 6 quark flavours: up, down, strange, charm, top and bottom. 

The strong nuclear force is the force that acts between quarks and holds the nucleus together.

Leptons (such as the electron) are particles that are unaffected by the strong nuclear force.

Hadrons (such as the neutrons) are particles that consist of quarks and hence are affected by the strong nuclear force.

PHYSICS IMPORTANT NOTES:

Particle	Relative mass	Charges
Proton (p)	1	+e
Neutron (n)	1	0
Electron (e)	0.0005	-e
Alpha Particle (α)	4	+2e

Up	Down	Charm	Strange	Top	Bottom
+ 2/3 e	-1/3 e	+ 2/3 e	-1/3 e	+ 2/3 e	-1/3 e
Anti-up	Anti-down	Anti-charm	Anti-strange	Anti-top	Anti-bottom
-2/3 e	+ 1/3 e	-2/3 e	+ 1/3 e	-2/3 e	+ 1/3 e

 

Radiation	Symbol	Mass	Charge	Typical Speed
Alpha particle	α	4	+2e	Slow (106 m/s)
Beta – particle	β-	1/1840	-e	Fast (108 m/s)
Beta + particle	β+	1/1840	+e	Fast (108 m/s)
Gamma rays	γ	0	0	Speed of light (3 x 108 m/s)