Nuclear Force
Tuesday, January 26, 2010
<$BlogDateHeaderDate>
Mass Defect:Nuclei are made up of protons and neutron, but the mass of a nucleus is always less than the sum of the individual masses of the protons and neutrons which constitute it.
The difference between the calculated mass of the unbound system and experimentally measured mass of nucleus is called mass defect.
It is denoted by Δm.
Mass defect can be calculated as follows:
Mass defect = (calculated mass of the unbound system) - (measured mass of nucleus)
Δm = (sum of masses of protons and neutrons) - (measured mass of nucleus)
Example:
The mass of an atom at rest is often expressed using the unified atomic mass unit (u). This unit is defined as a twelfth of the mass of a free neutral atom of carbon-12, which is approximately 1.66 × 10−27 kg.
1u = 1.66 × 10−27 kg
An atom has a mass approximately equal to the mass number times the atomic mass unit.
Nuclear Binding Energy:
The mass defect is a measure of the binding energy because it simply represents the mass of the energy which has been lost to the environment after binding. This energy is a measure of the forces that hold the nucleons together, and it represents energy which must be supplied from the environment if the nucleus is to be broken up.
The amount of energy required to break the nucleus of an atom into its isolated nucleons is called nuclear binding energy.
Once the mass difference, called the mass defect or mass deficiency, is known, the binding energy can be easily calculated from:
Albert Einstein's mass–energy equivalence formula: E = mc2
Where, m is the mass loss and c is the speed of light.
Thus,
Nuclear Binding Energy,
E = Δm x c2
where Δm is the mass defect.
Example:
Calculate the binding energy for alpha particle?
= 0.03035 u
= 0.03035 x 1.66054 x 10−27 kg
= 0.050397 x 10−27 kg
Binding Energy, E = 0.050397 x 10−27 kg x (3 x 108)2
= 0.453573 x 10−11 J
Nuclear force:
The energy which holds the nucleons together in a nucleus is the binding energy. This binding energy results in a strong attractive force between nucleons. This force is called nuclear force. Thus nuclear force can be defined as:
The strong attractive force which holds the nucleons together in the nucleus of an atom is called nuclear force.
Characteristics:
· Nuclear force is a short range force.
· If the distance between nucleons is longer beyond about 1.7 femtometer (fm) separation, the nuclear force is zero and if it is closer, the nuclear force acts as a powerful repulsive force.
· Nuclear force is independent of charge.
· Nuclear force is the same between any pair of nucleons. It is nearly independent of whether the nucleons are neutrons or protons.
posted by Lekshmi @ 11:03 AM,
0 Comments:
Post a Comment