In Greek, “same place” reads as
$\stackrel{`}{\iota}\sigma o\varsigma $$\tau \stackrel{`}{o}\pi o\varsigma $ (isos topos). This is why atoms which have the same number of protons, but
different numbers of neutrons, are called
isotopes . They are in the same place on the Periodic Table!
The following worked examples will help you to understand the concept of an isotope better.
For the element
${}_{92}^{234}\mathrm{U}$ (uranium), use standard notation to describe:
the isotope with 2 fewer neutrons
the isotope with 4 more neutrons
We know that isotopes of any element have the
same number
of protons (same atomic number)in each atom, which means that they have the same chemical symbol. However, they have a different number of neutrons, and therefore a different mass number.
Therefore, any isotope of uranium will have the symbol:
$$\mathrm{U}$$
Also, since the number of protons in uranium isotopes is always the same, we can write
down the atomic number:
$${}_{92}\mathrm{U}$$
Now, if the isotope we want has 2 fewer neutrons than
${}_{92}^{234}\mathrm{U}$ ,
then we take the original mass number and subtract 2, which gives:
$${}_{92}^{232}\mathrm{U}$$
Following the steps above, we can write the isotope with 4 more neutrons as:
$${}_{92}^{238}\mathrm{U}$$
Which of the following are isotopes of
${}_{20}^{40}\mathrm{Ca}$ ?
${}_{19}^{40}\mathrm{K}$
${}_{20}^{42}\mathrm{Ca}$
${}_{18}^{40}\mathrm{Ar}$
We know that isotopes have the same atomic number but different mass numbers.
You need to look for the element that has the same atomic number but a different atomic mass number. The only element is
${}_{20}^{42}\mathrm{Ca}$ . What is different is that there are 2 more neutrons than in the original element.
For the sulphur isotope
${}_{16}^{33}\mathrm{S}$ , give the number of...
protons
nucleons
electrons
neutrons
$Z=16$ , therefore the number of protons is 16 (answer to (a)).
$A=33$ , therefore the number of nucleons is 33 (answer to (b)).
The atom is neutral, and therefore the number of electrons is the same as the number of protons. The number of electrons is 16 (answer to (c)).
Atom A has 5 protons and 5 neutrons, and atom B has 6 protons and 5 neutrons. These atoms are...
allotropes
isotopes
isomers
atoms of different elements
For the sulphur isotopes,
${}_{16}^{32}\mathrm{S}$ and
${}_{16}^{34}\mathrm{S}$ , give the number of...
protons
nucleons
electrons
neutrons
Which of the following are isotopes of
${}_{17}^{35}\mathrm{Cl}$ ?
${}_{35}^{17}\mathrm{Cl}$
${}_{17}^{35}\mathrm{Cl}$
${}_{17}^{37}\mathrm{Cl}$
Which of the following are isotopes of
$\mathrm{U-}235$ ? (X represents an element symbol)
${}_{92}^{238}\mathrm{X}$
${}_{90}^{238}\mathrm{X}$
${}_{92}^{235}\mathrm{X}$
Relative atomic mass
It is important to realise that the atomic mass of isotopes of the same element will be different because they have a different number of nucleons. Chlorine, for example, has two common isotopes which are chlorine-35 and chlorine-37. Chlorine-35 has an atomic mass of 35 u, while chlorine-37 has an atomic mass of 37 u. In the world around us, both of these isotopes occur naturally. It doesn't make sense to say that the element chlorine has an atomic mass of 35 u, or that it has an atomic mass of 37 u. Neither of these are absolutely true since the mass varies depending on the form in which the element occurs. We need to look at how much more common one is than the other in order to calculate the
relative atomic mass for the element chlorine. This is the number that you find on the Periodic Table.
Questions & Answers
can someone help me with some logarithmic and exponential equations.
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
can nanotechnology change the direction of the face of the world
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.