Bcoz calcium is metal it forms ionic bond with oxygen by donating electrims by not sharing of electrons

Covalent bonds occur when two atoms share electrons in order to achieve a full outer electron shell. This type of bond is typically formed between nonmetals or nonmetallic elements. Let's analyze each option to determine which one is not likely to form a covalent bond.

A) Br: Bromine is a nonmetal and is located in Group 17 of the periodic table. It has 7 valence electrons and needs only one more electron to complete its outer electron shell. Therefore, it is likely to form a covalent bond by sharing one electron with another atom.

B) SiF4: Silicon tetrafluoride consists of one silicon atom and four fluorine atoms. Silicon is a metalloid and has 4 valence electrons, while fluorine is a nonmetal and has 7 valence electrons. In this compound, silicon can share its 4 valence electrons with the 4 fluorine atoms, forming covalent bonds.

C) CaO: Calcium oxide is composed of one calcium atom and one oxygen atom. Calcium is a metal and oxygen is a nonmetal. Metals tend to lose electrons, while nonmetals tend to gain electrons. In this case, calcium would lose two electrons to achieve a stable electron configuration, while oxygen would gain two electrons. This ionic interaction results in the formation of an ionic bond, not a covalent bond. Therefore, option C is the correct answer.

D) CH4: Methane is a compound consisting of one carbon atom and four hydrogen atoms. Carbon is a nonmetal with 4 valence electrons, while hydrogen is also a nonmetal with 1 valence electron. Carbon shares one electron with each of the four hydrogen atoms, resulting in a covalent bond.

In summary, option C (CaO) is not likely to form a covalent bond because it involves a metal (calcium) and a nonmetal (oxygen), leading to the formation of an ionic bond.