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
Is there any normative that regulates the use of silver nanoparticles?
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
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?