Ionic Or Covalent Bond

Explanation
CaO, also known as calcium oxide, is an ionic compound. Ionic compounds are formed when a metal and a non-metal combine through the transfer of electrons. In the case of CaO, calcium (a metal) donates two electrons to oxygen (a non-metal), resulting in the formation of an ionic bond. Ionic compounds typically have high melting and boiling points, and they conduct electricity when dissolved in water. Therefore, based on the properties and composition of CaO, it can be concluded that it is an ionic compound.

Explanation
SO2 is a molecule composed of one sulfur atom bonded to two oxygen atoms. In a covalent bond, atoms share electrons to achieve a stable electron configuration. Since sulfur and oxygen are both nonmetals, they have similar electronegativities and tend to share electrons rather than transfer them. Therefore, the correct answer is covalent.

Explanation
HNO6 is an ionic compound. Ionic compounds are formed by the transfer of electrons from one atom to another, resulting in the formation of ions with opposite charges. In the case of HNO6, the hydrogen atom donates its electron to the nitrogen atom, forming a positively charged hydrogen ion (H+) and a negatively charged nitrate ion (NO6-). Therefore, HNO6 is an ionic compound.

Explanation
KCl is an ionic compound because it is formed by the transfer of electrons from the metal element, potassium (K), to the non-metal element, chlorine (Cl). This transfer of electrons creates positively charged potassium ions and negatively charged chloride ions, which are held together by strong electrostatic forces of attraction. Ionic compounds typically have high melting and boiling points, are soluble in water, and conduct electricity when dissolved or molten.

Explanation
O2 refers to molecular oxygen, which consists of two oxygen atoms bonded together. Covalent bonding occurs when atoms share electrons, and in the case of O2, the two oxygen atoms share a pair of electrons. Therefore, the correct answer is covalent, as O2 is a covalent molecule.