Table of Contents
What is meant by expanded octet?
Main group elements that form more bonds than would be predicted by the octet rule are called hypervalent compounds, and have what is known as an ‘expanded octet,’ meaning that there are more than eight electrons around one atom.
How do you know when to expand an octet?
An atom like phosphorus or sulfur which has more than an octet is said to have expanded its valence shell. This can only occur when the valence shell has enough orbitals to accommodate the extra electrons. For example, in the case of phosphorus, the valence shell has a principal quantum number n = 3.
Why does sulfur have an expanded octet?
Since sulfur now has more than 8 electrons, we say that it “expands octet”. 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.
What is incomplete octet explain with example?
In chemical bonding: Incomplete-octet compounds. Less common than hypervalent compounds, but by no means rare, are species in which an atom does not achieve an octet of electrons. Such compounds are called incomplete-octet compounds. An example is the compound boron trifluoride, BF3, which is used as an industrial…
Is NH3 expanded octet?
Thus every atom in this stable molecule fulfills the octet rule. Nitrogen, the next nonmetal, has 5 electrons in the valence shell, so it needs to combine with 3 hydrogen atoms to fulfill the octet rule and form a stable compound called ammonia (NH3).
Which period elements can expand octet?
An element from Period 3 and below will be able to expand octet by making use of its energetically accessible, or low lying d-subshell for bonding. This means only Period 2 elements such as C, N, O and F cannot expand octet and have to obey octet rule.
Which of these elements is most likely to exhibit an expanded octet in its compounds?
The octet rule can be ‘expanded’ by some elements by utilizing the d- orbitals found in the third principal energy level and beyond. Sulfur, phosphorus, silicon, and chlorine are common examples of elements that form an expanded octet.
Can oxygen form an expanded octet?
Atoms with an expanded octet Phosphorous often has 5 orbitals (10 electrons) and sulfur often has 6 orbitals (12 electrons) because they are in the third period, but nitrogen and oxygen can never have expanded octets because they are in the second period and there is not such thing as a 2d orbital.
What are two atoms that comply with the octet rule?
The molecules of the halogens, oxygen, nitrogen, and carbon are known to obey the octet rule. In general, the elements that obey this rule include the s-block elements and the p-block elements (except hydrogen, helium, and lithium).
What does it do to complete the octet?
Chem – Completing the Octet Represent bonds as lines. Many teachers say to use dots instead of lines for bonds. When you draw a bond (with a line) immediately delete or draw over the 2 electrons that the bond is representing. Complete the octet of the outer atoms first. Only form one bond at a time and then count the octet.
What atoms are exceptions to the octet rule?
The most common exception to the octet rule is a molecule or an ion with at least one atom that possesses more than an octet of electrons. Such compounds are found for elements of period 3 and beyond.
What are two common exceptions to the octet rule?
However, there are three general exceptions to the octet rule: (1) molecules, such as NO, with an odd number of electrons; (2) molecules in which one or more atoms possess more than eight electrons, such as SF6; and (3) molecules such as BCl3, in which one or more atoms possess less than eight electrons.