For example: Looking at the periodic table, you can see that Oxygen has 8 electrons. Based on the order of fill above, these 8 electrons would fill in the following order 1s, 2s and then 2p. So Oxygen's electron configuration would be O 1s22s22p4.
In this sense the third shell can hold 8 electrons. In this sense the third shell can hold a total of 18 electrons. So the third shell can be considered to hold 8 or 18 electrons but in total the third shell can hold 18 electrons.
The octet rule refers to the tendency of atoms to prefer to have eight electrons in the valence shell. When atoms have fewer than eight electrons, they tend to react and form more stable compounds.
The third shell of an atom has 18 electrons only not 8 electrons. You might be confused because first the electrons of 4s are filled and then the 10 electrons of 3d shells are filled.
This principle states that, “Electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. In this way, the electrons of an atom or ion form the most stable electron configuration possible.” This is the reason for Calcium to have a configuration of 2,8,8,2 instead of 2,8,10.
This first shell has only one subshell (labeled 1s) and can hold a maximum of 2 electrons. This is why there are two elements in the first row of the periodic table (H & He). Because the first shell can only hold a maximum of 2 electrons, the third electron must go into the second shell.
Sulfur has one more electron pair in its 3s subshell so it can undergo excitation one more time and place the electron in another empty 3d orbital. Now sulfur has 6 unpaired electrons which means it can form 6 covalent bonds to give a total of 12 electrons around its valence shell.
Generally, the maximum number of electrons that the outermost shell of an atom can have is 8 (eight).
Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2) electrons.
It actually bonds. It will hold more than 8 electrons. Xenon having valence electrons in the 4th energy level, will also have access to the 4d sublevel, thus allowing for more than 8 electrons. XeF4is d2sp3 hybridized and contains 2 lone pair and 4 bonding pairs of valence electrons around the Xenon.
