Eight Electrons
Neon, with eight electrons in its outermost shell, is very stable and does not react. Second-period atoms try to reach that same configuration by sharing, giving up or accepting electrons: this is the octet rule.
Another goal: the configuration of Ne
Neon (1s2 2s2 2p6) has two electrons in the s orbital of shell 1, two electrons in the s orbital of shell 2 and six electrons in the p orbital of shell 2. This electronic situation is so stable that neon does not combine with any atom.
Important: shell 1 orbitals have been omitted. The shell 2 orbitals have been separated to give more clarity to the drawing. They would all be superimposed, around the 10-proton nucleus.
Share, share, share…
Atoms such as boron, carbon, nitrogen and oxygen, which lack electrons to acquire the neon configuration, achieve it by sharing electrons with other atoms.
Thus these atoms form chemical bonds. Each chemical bond is made up of the sharing of two electrons. Look how...
Outermost atomic orbitals of the element Boron
Important: shell 1 orbitals have been omitted. The shell 2 orbitals have been separated to give more clarity to the drawing. They would all be superimposed, around the 5-proton nucleus.
One way to simplify: We represent the symbol with its outermost electrons
Boron can combine with three hydrogens.
This is how it gets closer to its "goal" of having eight electrons around it, like neon
Outermost atomic orbitals of the element Carbon
Important: shell 1 orbitals have been omitted. The shell 2 orbitals have been separated to give more clarity to the drawing. They would all be superimposed, around the 6-proton nucleus.
One way to simplify:
To study the bonds between atoms, it is only interesting to consider the electrons in the outermost shell.
Carbon combines with four hydrogens.
Thus it achieves the "goal" of having eight outer electrons around it.
Outermost atomic orbitals of the element Nitrogen
Important: shell 1 orbitals have been omitted. The shell 2 orbitals have been separated to give more clarity to the drawing. They would all be superimposed, around the 7-proton nucleus.
One way to simplify:
To study the bonds between atoms, it is only interesting to consider the electrons in the outermost shell.
Nitrogen only needs to bond to three hydrogens to have eight electrons.
Thus it achieves the "goal" of having eight outermost electrons around it, leaving two unshared electrons.
Outermost atomic orbitals of the element Oxygen
Important: shell 1 orbitals have been omitted. The shell 2 orbitals have been separated to give more clarity to the drawing. They would all be superimposed, around the 8-proton nucleus.
One way to simplify:
To study the bonds between atoms, it is only interesting to consider the electrons in the outermost shell.
Oxygen only needs to bond to two hydrogens.
Thus it achieves the "goal" of having eight outermost electrons around it, leaving two pairs of unshared electrons.
Down here you can see the molecules formed and move them. Do they seem beautiful to you? Do they have the same shape? Click with the left button on a molecule and, holding it down, move the mouse. The molecule will move. If you press the right button, certain options will appear. Try them.
Give
Sodium and magnesium have complete electron shells 1 and 2 and one and two electrons, respectively, in the s orbital of shell 3. It is very easy for them to completely give up one electron (sodium) or two (magnesium) to another atom that readily accepts them. Sodium and magnesium form bonds by giving up electrons, not by sharing.
Accept
For its part, fluorine lacks one electron to have complete shell 2.
It is very easy for it to accept an electron from another atom that gives it up easily to achieve the neon configuration.
Fluorine forms bonds by accepting electrons.
Atoms, through three different methods of forming bonds with other atoms (sharing, transfer and electronic acceptance) manage to obtain, when forming a molecule, the configuration of the closest noble gas, which has the complete or "closed" outermost electronic shell with eight electrons.
Atoms form molecules by trying to surround themselves with eight electrons in their outermost shell.
This is called the octet rule.