International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

What is the dot and cross diagram for water, H₂O, used to illustrate?

1. The ionic character of water molecules

2. The covalent bonds formed between hydrogen and oxygen

3. The hydrogen bonding in water

4. The polar nature of water molecules

The correct answer is: The covalent bonds formed between hydrogen and oxygen

The correct answer highlights the primary focus of the dot and cross diagram for water, H₂O, which is to illustrate the covalent bonds formed between hydrogen and oxygen atoms. In a dot and cross diagram, dots and crosses represent the outer shell electrons from different atoms. For water, the diagram shows how one oxygen atom shares electrons with two hydrogen atoms, forming two covalent bonds. This sharing of electrons allows each hydrogen atom to achieve a stable electron arrangement, as do the electrons surrounding the oxygen atom. By depicting these shared electrons, the diagram effectively illustrates how covalent bonding occurs within the water molecule, showcasing the connectivity and electron sharing that defines the molecule's structure. The other options do touch on important concepts related to water, but they are not the primary focus of the dot and cross diagram. Ionic character, hydrogen bonding, and the polar nature of water can be discussed in other contexts or diagrams but are not the main aspect illustrated by the covalent representation in a dot and cross diagram.