<< Chapter < Page Chapter >> Page >
  • 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 ( α size 12{α} {} , β size 12{β} {} and γ size 12{γ} {} )? Why are nuclear decay energies so large? Pursuing natural questions like these has led to far more fundamental discoveries than you might imagine.

The first image shows a lump of coal. The second image shows a pair of hands holding a metal uranium disk. Third image shows a cylindrical glass tube containing slivery-brown cesium.
Why is most of the carbon in this coal stable (a), while the uranium in the disk (b) slowly decays over billions of years? Why is cesium in this ampule (c) even less stable than the uranium, decaying in far less than 1/1,000,000 the time? What is the reason uranium and cesium undergo different types of decay ( α size 12{α} {} and β size 12{β} {} , respectively)? (credits: (a) Bresson Thomas, Wikimedia Commons; (b) U.S. Department of Energy; (c) Tomihahndorf, Wikimedia Commons)

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 size 12{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 = 1836 m e size 12{m rSub { size 8{p} } ="1836" m rSub { size 8{e} } } {} (as noted in Medical Applications of Nuclear Physics and m n = 1839 m e size 12{m rSub { size 8{n} } ="1839" m rSub { size 8{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

1 u = 1 . 6605 × 10 27 kg. size 12{"1 u"=1 "." "6605"´"10" rSup { size 8{-"27"} } " kg"} {}

This unit is defined so that a neutral carbon 12 C atom has a mass of exactly 12 u. Masses are also expressed in units of 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 = mc 2 size 12{E= ital "mc" rSup { size 8{2} } } {} and units of m size 12{m} {} in MeV/ c 2 size 12{"MeV/"c rSup { size 8{2} } } {} , we find that c 2 size 12{c rSup { size 8{2} } } {} cancels and E size 12{E} {} comes out conveniently in MeV. For example, if the rest mass of a proton is converted entirely into energy, then

E = mc 2 = ( 938.27 MeV/ c 2 ) c 2 = 938.27 MeV. size 12{E= ital "mc" rSup { size 8{2} } = \( "938" "." "27" "MeV/"c rSup { size 8{2} } \) c rSup { size 8{2} } ="938" "." "27"" MeV"} {}

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

1 u = 931.5 MeV/ c 2 . size 12{"1 u"="931" "." 5" MeV/"c rSup { size 8{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 X N , size 12{"" lSub { size 8{Z} } lSup { size 8{A} } X rSub { size 8{N} } } {}

where the symbols A size 12{A} {} , X size 12{X} {} , Z size 12{Z} {} , and N size 12{N} {} are defined as follows: The number of protons in a nucleus is the atomic number     Z size 12{Z} {} , as defined in Medical Applications of Nuclear Physics . X is the symbol for the element , such as Ca for calcium. However, once Z size 12{Z} {} is known, the element is known; hence, Z size 12{Z} {} and X are redundant. For example, Z = 20 size 12{Z="20"} {} is always calcium, and calcium always has Z = 20 size 12{Z="20"} {} . N size 12{N} {} is the number of neutrons in a nucleus. In the notation for a nuclide, the subscript N size 12{N} {} is usually omitted. The symbol A size 12{A} {} is defined as the number of nucleons or the total number of protons and neutrons ,

Questions & Answers

do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
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
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
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 ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
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
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Berger describes sociologists as concerned with
Mueller Reply
4
Mykayuh Reply
Because I'm writing a report and I would like to be really precise for the references
Gre Reply
where did you find the research and the first image (ECG and Blood pressure synchronized)? Thank you!!
Gre Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Physics 101. OpenStax CNX. Jan 07, 2013 Download for free at http://legacy.cnx.org/content/col11479/1.1
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Physics 101' conversation and receive update notifications?

Ask