Which of the following must occur for elements to form a compound?

• A. The elements must have the same number of protons.
• B. A chemical bond must form between the atoms of the elements.
• C. The elements must be heated until they evaporate.
• D. The elements must be physically mixed without any interaction.

Answer: (B)

Verified step by step guidance

1. Understand that a compound is formed when two or more different elements chemically combine, meaning their atoms interact to form new substances with distinct properties.
2. Recognize that having the same number of protons (which defines the element) is not necessary for compound formation; elements with different numbers of protons can combine.
3. Know that simply heating elements until they evaporate or physically mixing them without interaction does not create a compound, as no chemical change or bonding occurs in these cases.
4. Identify that the key requirement for compound formation is the creation of a chemical bond between atoms of different elements, which involves sharing or transferring electrons.
5. Therefore, the essential condition for elements to form a compound is that a chemical bond must form between their atoms.