Answer: only the molecules in option D are entirely ionic
Step-by-step explanation:
The question requires us to identify the option that presents only ionic molecules.
An ionic molecule is formed when its elements are bonded throught an ionic bond, or, in other words, when there is one element that "loses" its electrons while another element "receives" these electrons.
An ionic bond is usually formed between atoms that present a strong electronegativity difference. We can say that an ionic bond is usually formed between metals and non metals, exactly because metals tend to "donate" their electrons (forming cations), while non metals tend to "receive" electrons (forming anions).
Analyzing the options given by the question, we can make the following remarks:
- NO2, CO2 and SO2 are classic covalent compounds - the electronegativity difference between the atoms that form this molecule is not high (we can see it by their position in the periodic table, as N, C and S are all close to O). With this information, we can already rule out options A, B and C;
- the compounds CsCl and KCl are classic ionic compounds, as they are formed by a metal (Cs and K) and a non metal (Cl);
- the metal Mn in the compound MnO3 presents oxidation number +6 (keep in mind that the oxidation number of O is usually -2, thus with 3 O atoms in the molecule, Mn must present valence +6 to form a neutral molecule). These two atoms form a bond with a strong ionic character.
Therefore, we can say that only the molecules in option D are entirely ionic.