Prelims - Nucleus

Nucleus

Center of the atom and contains the protons and neutrons.

Nucleons

Protons and neutrons are collectively known as

Protons

The number of \_____ determines the element

Greater

The number of neutron is always \_____ that the number of protons.

quarks, anti-quarks and gluons

Protons and neutrons are made up of combination of

+2/3

Charge of up quark

-1/3

Charge of down quark

2 up and 1 down

Protons contain 3 valence quarks

2 down and 1 up

Neutrons contain 3 valence quarks

Liquid Drop Model

Assumes a spherical nucleus composed of closely packed nucleons.

Neils Bohr

Liquid Drop Model is introduced by who?

Shell Model

Protons and neutrons occupy shells and subshells that are arranged in discrete energy shells.

Maria Goeppert-Mayer

Shell Model is introduced by who?

Nuclear binding energy

is the work (energy) required to overcome the strong nuclear force.

Mass defect

is the difference between the sum of the masses of all nucleons to the measured mass of the nucleus. The energy equivalence of this mass is equal to the nuclear binding energy.

E \= mc2

Mass-Energy relationship in nucleus

Nuclear Stability

There are very large repulsive electrostatic forces between protons which should cause the nucleus to fly apart

strong nuclear force

The nuclei are stable because of the presence of a shortrange

stable

up to atomic number 82 (lead)

unstable

technetium (Z \= 43) and promethium (Z \= 61)

unstable

Larger atoms (Z \> 83)

Belt or Band of Stability

Neutron-Proton ratio chart

Positive

charge of a nucleus

Magic Numbers

natural occurrences in isotopes that are particularly stable, and include Z \= 2, 8, 20, 28, 50, 82, 114 N \= 2, 8, 20, 28, 50, 82, 126, 184

True

Nuclear binding energy typically ranges from 6 to 9 MeV

True

In nuclear reactions, any change in the mass of the nuclei has an associated change in its energy

False

Lead with an atomic number of 82 is unstable

False

In larger atoms, protons exceed the number of neutrons

True

Protons and neutrnos are no longer believed to be a fundamental principle

False

Neutrons contain 2 up quark and 1 down quark

False

Nucleus with 2, 8, 20, 50, 82, or 126 protons or neutrons are considered unstable nucleus