Sunday, February 12, 2017

The First Helium Compounds

Can helium form compounds?
Helium, He, is the first Group 18 element or Noble Gas element.
In the nucleus of a helium atom there are 2 protons, and surrounding the nucleus there are just 2 electrons. These 2 electrons complete the first energy level and require large amounts of energy to remove. For this reason, an atom of helium is very stable and does not undergo chemical reactions on Earth.
But what if you tried to react helium, a non-metal, with a highly reactive metal, such as sodium, at extremely high pressures (greater than 113 GPa)?
Utah University Chemists predicted that under these conditions helium and sodium would form a compound. Then, high pressure synthesis in a diamond anvil actually produced a stable compound with the formula Na2He.
On the left hand side is a "ball and stick" model of Na2He in which the purple balls represent sodium and the white balls represent helium.You can see that the structure is cubic.
On the right hand side is a polyhedral representation of Na2He in which sodium atoms form the cubes (Na8). Half of these cubes are occupied by helium atoms, and these are shown as grey boxes. But the other half of the cubes are occupied by 2 electrons and these are shown in the diagram as red spheres.
The chemists are predicting that other compounds of helium may also be possible, such as Na2HeO.

Reference:
 Utah State University. "Up, up and away: Chemists say 'yes,' helium can form compounds: Helium and sodium form stable compound at high pressure." ScienceDaily. www.sciencedaily.com/releases/2017/02/170206111848.htm (accessed February 12, 2017).

Further Reading:
Introduction to the Modern Periodic Table 
 Bohr Model of the Atom 
Evidence for Electron Configuration of an Atom
Subshell Electronic Configuration

Suggested Study Questions:
  1. What is the atomic number for
    • helium
    • sodium
  2.  How many electrons are present in an atom of
    • helium
    • sodium
  3.  Write the simple electronic configuration for an atom of each element below:
    • helium
    • sodium
  4.  Write the electron configuration for an atom of each element below using subshell notation:
    • helium
    • sodium
  5. Write an equation for the loss of an electron from a gaseous atom of sodium. 
  6. Give the simple electronic configuration for the ion of sodium produced above.
  7. Give the electronic configuration of the sodium ion produced above in terms of subshells.
  8. Explain why the first ionisation of helium is so much higher than the first ionisation energy of sodium.
  9. Explain why sodium readily forms compounds.
  10. Explain why it is extremely difficult to produce helium compounds, and why it has required such enormous pressures in order to produce the first helium compound.

Friday, February 3, 2017

Isoelectronic Species

What do we mean by two or more species being isoelectronic?
What are some examples of isoelectronic species?
I'm glad you asked!
AUS-e-TUTE has just added a new tutorial, game, test and exam to help you understand this.
AUS-e-TUTE Members should log-in to use the new resources:
http://www.ausetute.com.au

Not a member?
A "free-to-view" tutorial is currently available for evaluation purposes at:
http://www.ausetute.com.au/isoelectronic.html

Sunday, January 15, 2017

Problem Solving in Chemistry

Some years ago, AUS-e-TUTE added a "how to solve problems in chemistry" page.
We call this approach to problem solving the StoPGoPS method:
  1. Stop: State the question.
  2. Pause: Prepare a plan of how you will solve the problem'
  3. Go! Follow the steps in your plan.
  4. Pause: Ponder the plausibility of your answer. (Have you answered the question you were asked? Does the answer look "about right"?
  5. Stop: State your solution (if your answer seems plausible) or Start again (if your answer doesn't look right)
Well, we have now added a Template that students can use to help guide them through the Problem Solving Process. You can download this "Template for Problem Solving" pdf at ausetute.com.au for free.

Monday, January 2, 2017

2017 Calendar

AUS-e-TUTE's 2017 Calendar, designed just for Chemistry Students, is now available as a FREE pdf.
Go to www.ausetute.com.au and click the links to download the calendar.

Wednesday, December 7, 2016

Molecular Machines



People use machines to perform tasks that fall beyond our capacities.
Since the Industrial Revolution, the complexity and number of machines we use has increased.
At the Annual Meeting of the American Physical Society in 1959, physicist and 1965 Nobel Laureate in Physics, Richard Feynman talked about the possibility of building small machines from atoms.
He returned to this idea in a lecture in 1984 he asked, "How small can you make a machine?".
But by then Chemists had already taken the first tentative steps towards building molecular machines.
The 2016 Nobel Prize in Chemistry has been awarded to Jean-Pierre Sauvage, Sir J. Fraser Stoddart and Bernard L. Feringa, whose research has led to the development of molecular machines...

Learn more in this edition of AUS-e-NEWS.

Visit http://www.ausetute.com.au/ausenews.html to subscribe to AUS-e-NEWS, AUS-e-TUTE's free quarterly newsletter.

Saturday, November 12, 2016

Fatty Acids

Do you want to answer any of the questions listed below:
  • What is a fatty acid?
  • What are the structures and formulae of common fatty acids?
  • What is a saturated fatty acid?
  • What is an unsaturated fatty acid?
  • What is a monounsaturated fatty acid?
  • What is a polyunsaturated fatty acid?
  • What determines the melting point and solubility of a fatty acid?
  • What is an essential fatty acid?
  • What is an omega-3 fatty acid?
  • What is an omega-6 fatty acid?
AUS-e-TUTE has new resources to help you answer these questions!
AUS-e-TUTE Members should log-in to use the new tutorial, game, test and exam.

If you are not an AUS-e-TUTE Member, a "free-to-view" Fatty Acids tutorial is currently available at http://www.ausetute.com.au/fattyacid.html for evaluation purposes.

Friday, October 21, 2016

Vitamins

Does it seem that dieticians and nutrition experts seem to make a huge fuss about eating foods that seem to contain infinitesimal amounts of those mysterious substances known as vitamins?
Well, there is some good, sound chemistry behind why this is so.
Find out about the chemistry of vitamins with AUS-e-TUTE's newest set of resources!

Members should log-in to access the Vitamins tutorial, game, test and exam.

If you are not an AUS-e-TUTE Member, a free-to-view tutorial is currently available for evaluation purposes at: http://ausetute.com.au/vitamincd.html