# 11.5 Substructure of the nucleus

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• Define and discuss the nucleus in an atom.
• Define atomic number.
• Define and discuss isotopes.
• Calculate the density of the nucleus.
• Explain nuclear force.

What is inside the nucleus? Why are some nuclei stable while others decay? (See [link] .) Why are there different types of decay ( $\alpha$ , $\beta$ and $\gamma$ )? Why are nuclear decay energies so large? Pursuing natural questions like these has led to far more fundamental discoveries than you might imagine.

We have already identified protons    as the particles that carry positive charge in the nuclei. However, there are actually two types of particles in the nuclei—the proton and the neutron , referred to collectively as nucleons    , the constituents of nuclei. As its name implies, the neutron    is a neutral particle ( $q=0$ ) that has nearly the same mass and intrinsic spin as the proton. [link] compares the masses of protons, neutrons, and electrons. Note how close the proton and neutron masses are, but the neutron is slightly more massive once you look past the third digit. Both nucleons are much more massive than an electron. In fact, ${m}_{p}=\text{1836}{m}_{e}$ and ${m}_{n}=\text{1839}{m}_{e}$ .

[link] also gives masses in terms of mass units that are more convenient than kilograms on the atomic and nuclear scale. The first of these is the unified atomic mass    unit (u), defined as

$\text{1 u}=1\text{.}\text{6605}×{\text{10}}^{-\text{27}}\phantom{\rule{0.25em}{0ex}}\text{kg.}$

This unit is defined so that a neutral carbon ${}^{\text{12}}\text{C}$ atom has a mass of exactly 12 u. Masses are also expressed in units of $\text{MeV/}{c}^{2}$ . These units are very convenient when considering the conversion of mass into energy (and vice versa), as is so prominent in nuclear processes. Using $E={\text{mc}}^{2}$ and units of $m$ in $\text{MeV/}{c}^{2}$ , we find that ${c}^{2}$ cancels and $E$ comes out conveniently in MeV. For example, if the rest mass of a proton is converted entirely into energy, then

$E={\text{mc}}^{2}=\left(\text{938.27 MeV/}{c}^{2}\right){c}^{2}=\text{938.27 MeV.}$

It is useful to note that 1 u of mass converted to energy produces 931.5 MeV, or

$\text{1 u}=\text{931.5 MeV/}{c}^{2}.$

All properties of a nucleus are determined by the number of protons and neutrons it has. A specific combination of protons and neutrons is called a nuclide    and is a unique nucleus. The following notation is used to represent a particular nuclide:

${}_{Z}^{A}{\text{X}}_{N},$

where the symbols $A$ , $\text{X}$ , $Z$ , and $N$ are defined as follows: The number of protons in a nucleus is the atomic number     $Z$ . X is the symbol for the element , such as Ca for calcium. However, once $Z$ is known, the element is known; hence, $Z$ and $\text{X}$ are redundant. For example, $Z=\text{20}$ is always calcium, and calcium always has $Z=\text{20}$ . $N$ is the number of neutrons in a nucleus. In the notation for a nuclide, the subscript $N$ is usually omitted. The symbol $A$ is defined as the number of nucleons or the total number of protons and neutrons ,

Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
what does nano mean?
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
it is a goid question and i want to know the answer as well
Maciej
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
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