Hydrogen duet rule

Arrange the remaining electrons around the atoms to satisfy the duet rule for hydrogen and the octet rule for other atoms. 

Because the maximum number of electrons in the first shell of an atom is 2, helium is stable with 2 electrons in its only occupied shell. The other very light elements—hydrogen, lithium, and beryllium—tend to form stable states by achieving the 2-electron configuration of helium. Having 2 electrons in the first shell, when that is the only shell and therefore the outermost shell, is a stable state, and the 2 electrons are sometimes called a duet. When there is only one shell, 2 electrons in that shell act like 8 electrons in any other outermost shell. Therefore, an atom with 2 electrons in its outermost first shell is often said to obey the octet rule, although duet rule would be more precise. 

Hydrogen forms stable molecules where it shares two electrons. That is, it follows a duet rule. For example, when two hydrogen atoms, each with one electron, combine to form fhe H2 molecule, we have... 

When atoms form covalent bonds, they try to attain a valence-electron configuration similar to that of the nearest noble gas element. Thus hydrogen in a bond would have two electrons (like helium, the duet rule) and others would have eight electrons (like neon and argon, the octet rule). 

Lewis structures are drawn to represent the arrangement of the valence electrons in a molecule. The rules for drawing Lewis structures are based on the observation that nonmetal atoms tend to achieve noble gas electron configurations by sharing electrons. This leads to a duet rule for hydrogen and to an octet rule for many other atoms. 

Duet rule With only a Is orbital capable of holding two electrons (Is, helium is simply too small to hold eight electrons like the rest of the noble gases. Likewise, hydrogen (Is ) wants just one electron to achieve Is, just as lithium (Is 2s ) wants to rid itself of the 2s electron to become Is. ... 

Example 1 Write the electronic formula for CH4O which satisfies the covalency requirements and the octet rule (duet rule for hydrogen). 

These examples illustrate the principle that atoms in covalently bonded species tend to have noble-gas electronic structures. This generalization is often referred to as the octet rule. Nonmetals, except for hydrogen, achieve a noble-gas structure by sharing in an octet of electrons (eight). Hydrogen atoms, in molecules or polyatomic ions, are surrounded by a duet of electrons (two). 

Atoms containing only Is electrons simply don t have eight slots to fill, so hydrogen and helium obey the duet (two) rule. They re perfectly happy with only two electrons. 

In drawing Lewis structures for covalently bonded molecules, the octet rule is used as a guide (remember that for hydrogen the octet is changed to a duet). Shared electrons count toward the electron total for both atoms in the bond. For example, the Lewis structure for SiH4 looks like this ... 

Arrange the remaining electrons as lone pairs or create double or triple bonds to satisfy the octet rule. Exceptions Hydrogen satisfies the duet (two) rule, and boron and aluminum satisfy the six-electron rule. 

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