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To hold positively charged protons together in the very small volume of a nucleus requires very strong attractive forces because the positively charged protons repel one another strongly at such short distances. The force of attraction that holds the nucleus together is the strong nuclear force    . (The strong force is one of the four fundamental forces that are known to exist. The others are the electromagnetic force, the gravitational force, and the nuclear weak force.) This force acts between protons, between neutrons, and between protons and neutrons. It is very different from the electrostatic force that holds negatively charged electrons around a positively charged nucleus (the attraction between opposite charges). Over distances less than 10 −15 meters and within the nucleus, the strong nuclear force is much stronger than electrostatic repulsions between protons; over larger distances and outside the nucleus, it is essentially nonexistent.

Nuclear binding energy

As a simple example of the energy associated with the strong nuclear force, consider the helium atom composed of two protons, two neutrons, and two electrons. The total mass of these six subatomic particles may be calculated as:

( 2 × 1.0073 amu ) + ( 2 × 1.0087 amu ) + ( 2 × 0.00055 amu ) = 4.0331 amu protons neutrons electrons

However, mass spectrometric measurements reveal that the mass of an 2 4 He atom is 4.0026 amu, less than the combined masses of its six constituent subatomic particles. This difference between the calculated and experimentally measured masses is known as the mass defect    of the atom. In the case of helium, the mass defect indicates a “loss” in mass of 4.0331 amu – 4.0026 amu = 0.0305 amu. The loss in mass accompanying the formation of an atom from protons, neutrons, and electrons is due to the conversion of that mass into energy that is evolved as the atom forms. The nuclear binding energy    is the energy produced when the atoms’ nucleons are bound together; this is also the energy needed to break a nucleus into its constituent protons and neutrons. In comparison to chemical bond energies, nuclear binding energies are vastly greater, as we will learn in this section. Consequently, the energy changes associated with nuclear reactions are vastly greater than are those for chemical reactions.

The conversion between mass and energy is most identifiably represented by the mass-energy equivalence equation    as stated by Albert Einstein:

E = m c 2

where E is energy, m is mass of the matter being converted, and c is the speed of light in a vacuum. This equation can be used to find the amount of energy that results when matter is converted into energy. Using this mass-energy equivalence equation, the nuclear binding energy of a nucleus may be calculated from its mass defect, as demonstrated in [link] . A variety of units are commonly used for nuclear binding energies, including electron volts (eV) , with 1 eV equaling the amount of energy necessary to the move the charge of an electron across an electric potential difference of 1 volt, making 1 eV = 1.602 × 10 –19 J.

Questions & Answers

what is E cell?
Michelle Reply
what is hydrocarbon
Sensible Reply
this is an organic compound that consist of hydrogen and ox
Okafor
why is isotonic solution the as blood
Hawa Reply
Elaborate more pls
Adeyinka
could you rephrase the question please?
Elaine
what is hydrocarbon? pls
Sensible
Hydrocarbon are organic compound consisting of hydrogen and carbon atoms
Adeyinka
thanks
Sensible
why is electrolytes really active in water
Sensible
relationship between an orbit and a shell
Hawa Reply
relationship between orbit and a shell
Hawa
What a homogenous mixture
Allison Reply
these are mixture of same substance or particles
INETIABOR
they are mixture of same particles or substance
INETIABOR
Define homologous series
Chizoba Reply
it is an organic compound having the same chemical properties which differs in a successive member of CH4
Okafor
when iron is exposed to moisture and it rusts,the value of deltaG for the reaction is
Mary Reply
negative
Max
table
Witszy
what is chemistry
Siyanbola Reply
it is a branch of science that deals with the mixture of chemicals and properties and uses of matter
Okafor
define aci according to Lewis
Ryhanna Reply
an acid is an electron pair acceptor according to lewis
Mary
What is a homogenous mixture
Allison
it is d mixture of d same substances or particle or compound
Okafor
homogenous is the combination or mixture of the same particle or compound
johnson
the third ionization energy of aluminium
sanmi Reply
name the allotrope of carbon used in gas masks
Moses Reply
Discuss the synthesis of sucrose
Ojiya Reply
What is a glycoside and discuss the formation
Ojiya
explain the transitioning of glucose molecules from Fischer projection of glucose to the Haworth projection
Rosey Reply
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hezekiah Reply
what are metalliod
hezekiah
Metalloids are substances having the characteristics of both metals and non-metals
Ngwesse
what is acid
Tobi
define acid according to lewis
Ryhanna
Acid is an electron acceptor
Adeyinka
Wat z quantum
Adeyinka
what is valency
odukoya Reply
The number of chemical bonds the atoms of a certain element can form.
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Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
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