Yesterday, we have discussed on the atomic number (Z) and atomic mass (A) that are related to a chemical element.
Today, we shall continue with the discussion on Isotopes where many students tends to lose marks in exams.
Definition of Isotopes:
–> Atoms of the same element with the same number of protons but different number of neutrons
Charareristics:
- Same proton or atomic number
- Different nucleon or mass number
- Same chemical properties (since chemical reactions involve electrons only)
- Slightly different physical properties (since relative masses of isotopes differ)
Just with the above information, it will allow you to score all the marks you need in examinations with questions related to Isotopes.
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Most elements are commonly made up of isotopes. Only a few elements exist without isotopes.
Hydrogen has 3 Isotopes, with mass numbers 1, 2 and 3. They contain the same number of protons and electrons, but differ in number of neutrons.
Hydrogen-1 has no neutrons, Hydrogen-2 has one neutron and Hydrogen-3 has two neutrons.
Let’s check out an exam-based question related to Isotopes.
Question 1:
Uranium-235 and uranium-238 are two isotopes of uranium.
The table below shows the numbers of the particles in one atom of uranium-235.Particle Number
Electron?? ?92
Neutron??? 143
Proton?????? 92(a) Define Isotopes.
(b) Suggest a reason why this is known as uranium-235.
(c) Give the numbers of particles found in an atom of uranium-238.
PS: Remember to leave your suggested answers in the “Leave A Reply” section below this post.
hi i emailed you a question and got no reply so plz help me out.i will be thankful to you.
Thanks sir,hope u visit srilanka………….
Hi shihana,
I would definitely love to visit Sri Lanka, a beautiful place to be in.
For 2009, we will not be conducting Chemistry Workshops outside of South-East Asia, as confirmed by my parent company WINNERS Education Group.
As such, the only way you can learn from me, is through this blogsite and / or we start the “Overseas Coaching” for overseas coaching.
Meanwhile, you can check out all the earlier archive blogposts on O Levels Chemistry Questions and participate in it. In addition, you can write me an email at sean@SimpleChemConcepts.com.
Hope this helps.
To Your Academic Success in Chemistry,
Sean Chua
Master Trainer & Author
WINNERS Education Group
?Experience Learning with A Difference?
Hi Michelle,
Answer for Part (C) is not correct.
Check out my answer below to timothy.
Thank you.
To Your Academic Success in Chemistry,
Sean Chua
Master Trainer & Author
WINNERS Education Group
?Experience Learning with A Difference?
Hi timothy,
Thank you for your comments.
For some reasons, i missed out your comment for 3 months! Gosh.
Hope this reply is still useful to you.
And regards to “mean”, dont worry. In our coaching (including this humble chemistry blogsite), we encourage cross-correction and participation, as we believe experiential learning is the most effective method of learning.
Back to your question, you are right. Michelle answer for Part (C) is not correct.
In this question (an O Level Chemistry Question), the “particle” in the questions actually refers to the “Sub-atomic particle” in atom. This meaning they are asking you the number of Protons + Electrons + Neutrons in the Uranium-238 atom.
Answer will therefore be = 92 (Protons) + 92 (Electrons) + 146 (Neutrons)
= 330
Hope this clarifies your doubt.
Look forward to hearing from you.
To Your Academic Success in Chemistry,
Sean Chua
Master Trainer & Author
WINNERS Education Group
“Experience Learning with A Difference”
hi mr.sean
i really have lot of doubts in chemistry,and i want to join your class,but how can i coz i’m in srilanka,pls help me coz i want a good grade in chemisrty.dont you like to visit srilanka
hi sean, great job u have this blog site to help students improve their chemistry grades.btw, can i clarify michelle’s answer for part c?
(c) Give the numbers of particles found in an atom of uranium-238.
is the answer 327?
does 1 atom equate to 1 mole of uranium?i’m just a little confused because it would be quite a feat if an atom cn have 6×10^23 particles.
hope u can respond to my query.i don’t mean to criticize anyone but just seeking for clarification.
thanks
Hi Garrick,
As i mentioned to Gary and Michelle, the physical properties are determined by many factors which you will learn at higher chemistry education. It is true when you compare one group to another in the Periodic Table, their physical properties such as density, electrical conductivity, colour etc are different.
But do note that Chemical Properties are also different when you compared one group to another group.
I would recommend that you understand and then memorise the GROUP PROPERTIES & TRENDINGS for Group I, VII, VIII and Transition Metals.
And to answer your question on Difference Between Physical & Chemical Properties, you have it below:
Physical Properties are properties of an element or compound that can be observed without a chemical reaction of the substance.
In a physical change, the substances are not altered chemically. No new products are formed. Chemical bonds are not broken in a physical change
A physical change can affect the size, shape or color of a substance but does not affect its composition. The substances may be changed to another phase (i.e. gas, liquid, solid) or separated or combined.
Examples of Physical Property:
1) Colour
2) Density
3) Melting and Boiling Point
4) Electrical conductivity
etc
Chemical Property is a characteristic of a substance that is observed when it undergoes a chemical change.
In a chemical change, the substances are altered chemically and display different physical and chemical properties after the change. When a chemical change occurs new substance(s) are formed through a reorganization of the atoms. A chemical change is irreversible.
Examples of Chemical Properties:
1) 2Mg + O2 –> 2MgO
2) Zn + 2HCl –> ZnCl2 + H2
3) N2 + 3H2 –> 2NH3
Hope this is useful to you. Study Hard!
Cheers,
Sean
PS: If you want to find out more about the Common Mistakes (Misconceptions) that most students made in chemistry exams, you can check out my new book.
Hi Gary,
You are absolutely spot on.
Physical Properties are not directly related to the number of neutrons.
There are more reasons to that, which are usually thought in higher chemistry education.
Rgds
Sean
Hi Michelle,
Great answers for the above posted question.
For your question, Physical Properties of an element are NOT related to its number of neutrons.
Different types of Physical Properties are due to different reasons such as Covalent Molecule or Ionic Compounds, Molecular Mass of Substance, Structure & Shapes, etc..You will learn this when you are going to study Chemistry in higher education.
Regards,
Sean
Hello.
I believe it has something to do with the arrangements in the periodic table, by that i mean in their specific groups or periods.
The word “properties” never cease to confuse me. I believe physical properties refer to colour, strength, density, e.g. However do you include bp and mp, and electrical conductivity? Then what do chemical properties stand for? Mind giving a list or a generic statement to help students like me differentiate between physical and chemical properties?
Thanks a lot for any form of help.
It is highly unlikely neutrons are related to the physical property of an element.
For example if you make a statement that ‘higher number of neutrons has a higher mp/bp’,and if you were to compare to compare, it is not true.
Similarly for the ability to conduct electricity.
Correct me if i am wrong Sean.Thank you=)
Question 1:
Uranium-235 and uranium-238 are two isotopes of uranium.
The table below shows the numbers of the particles in one atom of uranium-235.
Particle Number
Electron 92
Neutron 143
Proton 92
(a) Define Isotopes.
Isotopes are atoms of the same elements that have the same number of protons but different number of neutrons.
(b) Suggest a reason why this is known as uranium-235.
The sum of its protons and neutrons is 235.
(c) Give the numbers of particles found in an atom of uranium-238.
6 x 10^23 particles
* are the physical properties of an element are related to its number of neutrons?