Which compound is an exception to the octet rule?
h2o
hcl
ccl4
clf3

is an exception to the octet rule.

Further explanation:

Chemical bond:

The attraction between atoms, molecules or ions that is responsible for the formation of chemical compounds is known as a chemical bond. It is formed either due to electrostatic forces or by the sharing of electrons. There are many strong bonds such as ionic bonds, covalent bonds, and metallic bonds while some weak bonds like dipole-dipole interactions, London dispersion forces, and hydrogen bonding also exist.

Octet rule:

According to this rule, the elements have the tendency to bond with other elements in order to acquire eight electrons in their valence shells. This results in achieving a stable noble gas configuration. Generally, all elements obey octet rule but there are some exceptions to this rule. For example, Be and B do not follow the octet rule.

The atomic number of oxygen is 8 and therefore it has six valence electrons in it. The atomic number of hydrogen is 1 so it has only one valence electron in its valence shell. Oxygen needs two more electrons to fulfill its octet so it forms two single bonds with two hydrogen atoms. Therefore obeys the octet rule. (Refer to the structure in the attached image).

The atomic number of chlorine is 17 and therefore it has seven valence electrons in it. The atomic number of hydrogen is 1the so it has only one valence electron in its valence shell. Chlorine needs one more electron to fulfill its octet so it forms one single bond with a hydrogen atom. Therefore HCl obeys the octet rule. (Refer to the structure in the attached image).

The atomic number of chlorine is 17 and therefore it has seven valence electrons in it. The atomic number of carbon is 6 so it has four valence electrons in its valence shell. Each chlorine atom requires an electron to complete its octet. So four single bonds are formed between one carbon atom and four chlorine atoms. Therefore follows the octet rule. (Refer to the structure in the attached image).

The atomic number of chlorine is 17 and therefore it has seven valence electrons in it. The atomic number of fluorine is bond so it has seven valence electrons in its valence shell. Both chlorine and fluorine are just one electron short of the stable noble gas configuration. In , there is only one chlorine atom and three fluorine atoms so their octets cannot be fulfilled. But one chlorine atom can form only one bond with one fluorine atom. Therefore does not follow octet rule and hence is an exception to this rule. (Refer to the structure in the attached image).

Learn more:

1. Which molecule cannot be adequately described by a single Lewis structure/

2. Do carbon dioxide and water have the same geometry?

Answer details:

Grade: High School

Subject: Chemistry

Chapter: Chemical bonding and molecular structure

Keywords: H2O, HCl, CCl4, ClF3, octet rule, chemical bonds, hydrogen, chlorine, fluorine, carbon, 1, 8, 9, 17, one electron, seven electrons, six electrons, four electrons, exception.