Write the electron configuration showing the filling of sub-levels for Mg
Magnesium at its ground state has 12 electrons. To distribute the electrons to show the electronic configuration, we must follow the mnemonics:
`1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6...`
We should fill up the first sub level which is the `1s^2` sub level until the electrons are already distributed.
The electron configuration for magnesium (Mg) is written as:
`1s^2 2s^2 2p^6 3s^2`
To check if the electronic configuration is correct, count the number in the superscript if it equals the number of electrons of magnesium.
`1s^2, 2s^2, 2p^6 , 3s^2`
or you can get the answer by using the noble gas before the row where the elemement is found and shortcut the answer to :
1s2 2s2 2p6 3s2
The electron configuration for the element, Mg, is:
Note that when you add all the superscripts, they equal Mg's atomic number (or number of electrons).
`2+2+6+2 = 12`
A "shortcut" method for writing the electron configuration can also be:
This shows that the element has two (valence) electrons beyond the noble gas, Neon.
Lets take a look at the periodic table Mg sits in the 3s2 orbital. Now in order to write the full electron configuration we have to write all the full orbitals that come before 3s2. So you will start with the first full orbital of 1s2 and continue until you get 3s2 in increasing order. So 1s2 2s2 2p6 3s2 if you want to do it the short hand way you will have to choose the closest noble gas the element is towards then write the elements last full shell in this case it's neon. so [Ne] 3s2
`1s^(2) 2s^(2) 2p^(6) 3s^(2) or [Ne]3s^(2)`
On the periodic table, each column is given the letter s, p, d, or f and each row is given a number from 1 to 7, representing the energy levels. When doing electron configuration you start with the first element in the top left, hydrogen, and move left to right.
Mg is in the 3rd row which means you have to list the first two rows. The first row is represented with 1s^2. 1s means it is row one in the s-block or Alkali metals. The exponent 2 means that you have went two elements into the row. Now you continue with 2s^2 and 2p^6. The p-block is the main group elements. Finally you list 3s^2. This is where you stop because Mg is in row 3 and is the last element in the s-block.
Your electron configuration is `1s^(2)2s^(2)2p^(6)3s^(2)`