Level 2 Physics - Atomic physics

The 4 main features of Rutherfords expirement

Narrow tube for alpha particles, vacuum chamber, circular screen coated with zinc sulfide

The purpose of the narrow tube for alpha particles

to ensure alpha particles entered the chamber in a straight line

The purpose of the vacuum chamber

to ensure 4/2He2+ (alpha particles) did not ionsie the air(ie remove e- from molecules) to produce neutral helium atoms

The purpose of the circular screen

to detect alpha particles through a full 360o

The purpose of the Zince Sulfide coating on the circular screen

To detect alpha particles as there is a flash of light when alpha particles strike it

Rutherford made 3 observations what were they?

Most alpha particles went straight through, some alpha particles were deflected through large angles, some of the alpha particles were reflected straight back

Most alpha particles went straigth through

Most of the atom is empty space, there is a very small dense posetive nucleus

Some alpha particles were deflected through large angles

The posetive alpha particle was close enough to the gold nucleus to experience a force to repel it

Some alpha particles were reflected straight back

the posetive alpha particles were almost inline with a posetive nucleus and the repulsive force between the two posetive charges caused a dramatic change in direction

Isotope

Element that has the same atomic number(number of protons) but different number of neutrons(mass number)

Beta particle

When a neutron in a nuclear splits into a proton and electron. Electron given off as beta particle, proton stays in nucleus eq

Alpha particle

An alpha particle is a helium nucleus 4/2He. Number of protons decrease by 2 and protons and nucleus decrease by 4 producing a x nucleus (x)

Why does an alpha particle only travel a few cm in air

Alpha is posetively charged, it strips the air particles of the electrons to neutralise to the helium atom and ionise the air.