Octet Rule
The octet rule states that atoms tend to gain, lose, or share electrons in order to achieve a stable electron configuration with a full outer shell of eight electrons. This rule applies to most elements, particularly those in the second period (such as carbon, nitrogen, and oxygen) as well as elements in the third period and beyond.

A. XeF4
XeF4, or xenon tetrafluoride, is an example of a compound that does not obey the octet rule. Xenon is in the noble gas family and has a full outer shell with eight electrons. However, in XeF4, xenon forms four covalent bonds with four fluorine atoms, resulting in a total of 36 valence electrons around the central xenon atom. This exceeds the octet rule, as xenon now has 12 electrons in its outer shell.

B. AlCl3
AlCl3, or aluminum chloride, does not obey the octet rule either. Aluminum has three valence electrons, and in AlCl3, it forms three covalent bonds with three chlorine atoms. This results in a total of 18 valence electrons around the central aluminum atom, which is less than the octet rule.

C. SF6
SF6, or sulfur hexafluoride, does obey the octet rule. Sulfur has six valence electrons, and in SF6, it forms six covalent bonds with six fluorine atoms. This results in a total of 48 valence electrons around the central sulfur atom, satisfying the octet rule.

D. SCl2
SCl2, or sulfur dichloride, does not obey the octet rule. Sulfur has six valence electrons, and in SCl2, it forms two covalent bonds with two chlorine atoms. This results in a total of 18 valence electrons around the central sulfur atom, which is less than the octet rule.

Conclusion
Out of the given compounds, only SF6 follows the octet rule. XeF4, AlCl3, and SCl2 do not obey the octet rule due to the presence of more or fewer electrons than required to complete the octet.