Kaplan Nursing Entrance Practice Exam

When carbon atoms form long chains in different ways, these different forms are called:

1. Compounds

2. Isomers

3. Allotropes

4. Molecules

The correct answer is: Allotropes

When carbon atoms form long chains in different ways, the resulting different forms are referred to as isomers. Isomers are molecules that share the same molecular formula but have different structural arrangements. This variation can significantly affect the properties and reactivity of the substances. Carbon is unique in its ability to form various structures, including straight chains, branched chains, and rings due to its four valence electrons, allowing for diverse bonding configurations. The concept of isomerism highlights how the arrangement of atoms can lead to distinct chemical behaviors, which is essential in organic chemistry. While the other terms like compounds, allotropes, and molecules have their meanings, they do not accurately describe the specific phenomenon of varying structural forms of carbon chains. Compounds refer to substances composed of two or more different elements, allotropes typically denote different structural forms of the same element (like graphite and diamond for carbon), and molecules simply denote a group of atoms bonded together, which does not capture the concept of structural variation inherent in isomers.