Final answer:
Compounds like O2 and CO2 have low to no ionic character, while H2O has some polar covalent character. NaCl and KI, formed from a metal and a nonmetal, are predicted to have a high percentage of ionic character but it is not 100% due to the presence of covalent characteristics in some states.
Step-by-step explanation:
The percentage of ionic character in chemical compounds depends largely on the difference in electronegativity between the bonded atoms. Ionic compounds are usually formed when there is a complete transfer of electrons from one atom to another, typically between a metal and a nonmetal. Covalent compounds, on the other hand, involve the sharing of electrons between atoms.
- O2 is a diatomic molecule with no difference in electronegativity between the oxygen atoms, so it has 0% ionic character.
- CO2 consists of carbon and oxygen with a moderate difference in electronegativity, suggesting it has some polar character but is primarily covalent, not ionic.
- H2O (water) has polar covalent bonds due to the significant electronegativity difference between hydrogen and oxygen, but it's less than 50% ionic in character.
- NaCl has a high degree of ionic character, as sodium (a metal) transfers an electron to chlorine (a nonmetal), but it is not 100% ionic due to the presence of some covalent character in the gaseous state.
- KI, which forms between potassium (a metal) and iodine (a nonmetal), is predicted to be ionic and exhibits a high percentage of ionic character, though also not 100% due to similar reasons as NaCl.
Remember, determining the exact percentage of ionic character would require detailed measurements of dipole moments and bond distances, which goes beyond the scope of typical high school chemistry.