Electron Configuration

Hi there
I am really having difficulty understanding electron configuration and orbitals. I need someone to explain it, i.e. how the shape of the periodic table has to do with the orbitals, number of electrons per shell, shells... Could someone please explain, hopefully in an easy to understand way...

Any help is appreciated

Thanks

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http://www.webelements.com/forums/viewtopic.php?t=1538 see this post where I explain electron configuration.
the "s-block" of elements are the first to groups of alkali/alkali earth. They are named s because that is the outter most electron shell (valence shell where electron sharing takes place). The next group is the p block which lie on the far right from Boron to the noble gases....those elements possess p electrons on the outer most shell. Then the d's which are the transition elements from Sc to Zn. Sc has 1 electron in its d shell, and Zn has 10 of 10 electrons filled. Then finally the f-block aka lanthides/actinides. These have 14 electrons in the outer most shell (the f-shell).

Mendelev invented the periodic table.

What he did was basically lay out all the elements in an order, which put ones with similar chemical properties in vertical columns.
You can also spot trends in chemical behaviour up and down columns,
across rows, even diagonally sometimes.

This was in the 19th century, before anyone had discovered/and-or-invented-the-concepts of electrons, protons, neutrons, orbitals.

During the 20th century, these things were discovered, and it became apparent that chemical behaviour had a helluva lot to do with how the outermost electrons in an element's atoms behaved.
And what governed how they behaved had a helluva lot to do with what type of orbital they were in.
And, in a tremendous retrospective triumph for the long since dead Mr Mendelev, it turned out that his periodic table arrangment, with all those columns, corresponded nearly perfectly to how the underlying orbital were....

To understand what makes certain electrons in certain orbitals behave in certain ways, you need to use quantum mechanics - it will tell you stuff about energy, angular momentum, "spin", Pauli exclusion principles, and much more ........ but it's all rather complicated -)

One exception: Helium is from s-block, not p-block.

helium is an element,
and couldn't care less what way humans try to classify it!

It still fits perfectly into Mendelv's periodic table, at the top of the noble gasses group.

If I recal correctly, the noble gasses had not yet been discovered when Mendelev invented the table, so the whole group was added afterwards!
(Mendelev just had hyrdogren as an odd-one-out on its own)

The shape of the chart has changed over time as we have come to understand more about the causes for the recurrence of chemical properties. Mendeleev assumed that chemical properties were a periodic function of the atomic weight. When this didn't occur, Mendeleev resorted to two corrections; he proposed undiscovered elements (eka-boron, eka-aluminum, and eka-silicon (Sc, Ga, & Ge as it turned out) or claimed that the reported weights were wrong which works out except in one notorious exception, Ni has a lower atomic weight than Co. Enter the atomic number, which for Mendeleev was mostly a book-keeping procedure. We now see that the atomic number relates to the number of protons and electrons and therefore to the electron shells and the chemical properties and that the atomic weight is determined by protons + neutron and inconsequential in determining chemical properties, but a great scientific theory not only accounts for all of the observed phenomena, but is flexible enough to be revised in light of new data and leads to new insights. But anyone's estimation, Mendeleev's law is a first-rate theory. I only wish Md were a more interesting element.

The exception is strange enough. However I don't find Mendelevium interesting.

The exception of Ni and Co is only interesting if you believe that chemical properties are dependent on atomic weight; once you realize that the atomic number is the primary factor and that atomic weight is a secondary consequence, you can envision an element with 1 fewer proton than its neighbor but a few more neutrons and thus a higher atomic weight but lower atomic number; but it took quite a while for that reality to sink in.

When radioactivity was first discovered, Curie noted that Ra decayed into a gas which was called radon; but Ac also decays into a gas but with a different mass number (called actinon); in fact several investigators discovered several inert gasses with slightly different atomic weights; we of course realize that these are isotopes, differing in the number of nucleons but having tha same number of protons, and that lead to the final explanation of why Co and Ni are "exceptions" to Mendeleev's Law.

Re: Electron Configuration

[quote="petermc"]Hi there
I am really having difficulty understanding electron configuration and orbitals. I need someone to explain it, i.e. how the shape of the periodic table has to do with the orbitals, number of electrons per shell, shells... Could someone please explain, hopefully in an easy to understand way...

Any help is appreciated

Thanks[/quote]

Not to assist with the relationship between orbitals andthe periodic table - but at least I can show you the shapes of orbitals on my Orbitron site - see [url]http://www.shef.ac.uk/chemistry/orbitron/[/url]

So each bubble in the orbitron represents an orbit (2 electrons)?

Each orbital can contain two electrons (one electron has spin 'up', the other electron has spin 'down')

That's an excellent page - when I was a lad, we didn't have the computers available to draw complicated orbital shapes in 3 dimensions......
we had to make do with boring old black and white line drawings in textbooks - I'd never seen the g orbitals before - they're positively frightning! -O

Another thing to remember about all these wavefinction solutions is that in many cases, you can have real solutions or complex solutions - some are more useful than others when thinking about chemical behaviour......
goodness knows which ones the electrons find most useful though! wink

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