How are electronbs distributed in the different energy levels and orbitals??

Question

How are electronbs distributed in the different energy levels and orbitals??

Answer 1

A decent periodic table will list the way in which the orbital structures (energy levels) are built up sequentially, beginning with Hydrogen (1s1), He (1s2) and growing through levels s, p,d, and f in accordance with the Pauli exclusion principle and the oyher limitations on the values of the quantum numbers.

A good and not overly technical review can be found at:

http://www.chemguide.co.uk/atoms/propert...

For a more technical discussion check the Wikipedia entry.

Answer 2

This distribution is a consequence of 'Pauli's Exclusion Principle' (due to Wolfgang Pauli). It states that no two electrons in an atom occupy a single energy state dictated by the same set of quantum numbers.

Waht are these  quantum numbers?

1. the principal quantum number 'n', which is but the serial number of the orbit (the first orbit has n=1)

2. the orbital quantum number 'l': It is a function of ellipticity (specifically 'Eccentricity' of electron orbit) and is less than 'n'. Hence it takes values  

(n-1), (n-2), . . 2, 1, 0.

3. For every value of 'l' (and so it follows, for 'n' also), It is a matter of how the orbit is oriented in 3D space in relation to a reference plane of which it makes an angle and is labeled 'ml' (magnetic orbital quantum number). Consequently it takes values from 'l' to '-l' in unit decrements

l, (l-1), (l-2), . . 2, 1, 0, -1, -2, . . -(l-3), -(l-2), -(l-1), -l.

4. Now, every electron spins also. With right hand rule as a reference (for labeling its angular momentum vector) it is assigned a numerical value of 1/2, but with opposite signs; +1/2 & -1/2.

So, the logic is

n -> l -> ml  for two values of ms (=+1/2, -1/2)

Further, the orbital quantum number 'l' is a pointer to how much the electron orbit juts out of the confines of the atom. This importance is reflected in another set of labels 's'. 'p', 'd' & 'f' or 'sharp', 'principal', 'diffuse', or 'fundamental' specifically; that is a remnant of the enormous volume of spectroscopic work that was done before a definite model could emerge.

As an example take the first orbit:

n = 1

l = 0 only  { 's' electrons}

ml = 0 again

ms= +1/2, -1/2

s, p, d, f electrons are designated as per l = 1, 2, 3, 4 only. Situation of l = 5 (called 'g' electrons) is a recent phenomenon. It is revealing(and educative) if the electron configuration is figured out with periodic table in front. It revelas that 'f' electrons of 'Lanthanide' series impart strong magnetic properties because the electron orbits have maximum eccentricity; perhaps it can be extended to 'Actinide' series as well.  

To match my efforts, I strongly urge you to figure out the configuration for some more elements of periodic table like Sodium, Iron, Bromine etc.