Electrons levels and sublevels. Quantum number

Brainstorming

Make a list of inferences about any properties of objects in the box.
How could you learn more about the objects in the box without opening the box?
Scientist face these same questions as they try to learn more about atoms.

Quantum Numbers
Quantum numbers specify the address of each electron in an atom. There are four types of quantum numbers:
1. Principal quantum number, n → energy level (shell)
2. Secondary quantum number, l → subshell (s, p, d, f)
3. Magnetic quantum number, ml → orbital
4. Spin quantum number, ms → spin type of electro
There are no two electrons in an atom that can have the same four quantum numbers. Each electron has a unique address, like a family living in a flat. This is Pauli's Exclusion Principle.

1. The principal quantum number, n
determines the size and energy of an atom (larger n means bigger atoms and higher energy),
can take an integer value n = 1, 2, 3, 4 ... or (K, L, M, N...),
all electrons in an atom with the same value are said to belong to the same shell.

2. Secondary quantum number, l
determines the overall shape of the orbital within a shell
affects orbital energies (bigger l = higher energy)
all electrons in an atom with the same value of ‘l’ are said to belong to the same subshell
has integer values between 0 and n-1
may be called the “orbital angular momentum quantum number”

3. Magnetic quantum number, ml
determines the orientation of orbitals within a subshell does not affect orbital energy
has integer values between -I and +I
the number of ml values within a subshell is the number of orbitals within a subshell
s, p, d and f subshells includes 1, 3, 5 and 7 orbitals respectively.

4. Spin quantum number, ms
each orbital may contain two electrons at most several experimental observations can be explained by treating the electron as though it were spinning
spin affects the electron behave like a tiny magnet
spin can be clockwise (+1/2) or counterclockwise (-1/2)

Solving problems
Example 1
Find the values of quantum numbers for hydrogen atom.
Example 2
Show the values of possible quantum numbers for magnesium atom.( 12Mg)

Electron configuration
In 1925 Wolfgang Pauli stated his exclusion principle;
‘In the same atom, two electrons may not have identical sets of all quantum numbers.’
According to this principle, the quantum numbers, n, l, ml, and ms, can never be identical for two electrons in an atom.
The Aufbau process
The Aufbau principle basically states that the lowest energy orbitals are filled first.
Hund’s rule states that;
the electrons are distributed among the orbitals of a subshell of the same energy in a way that gives the maximum number of unpaired electrons with parallel spin.