A Level Chemistry OCR Practice Exam

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Prepare for the A Level Chemistry OCR Exam with quizzes. Study with flashcards, multiple choice questions, hints, and explanations. Enhance your understanding and boost your confidence for success!

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What does the atomic (proton) number indicate?

The number of neutrons in an atom
The number of protons in the nucleus of an atom
The total number of electrons in an atom
The number of energy levels in an atom

The correct answer is: The number of protons in the nucleus of an atom

The atomic number, also known as the proton number, specifically indicates the number of protons present in the nucleus of an atom. This fundamental characteristic defines the identity of the element; for example, all hydrogen atoms have an atomic number of 1 due to having one proton, while carbon has an atomic number of 6, indicating six protons in its nucleus. Understanding that the atomic number determines the number of protons is crucial, as it also indirectly indicates the number of electrons in a neutral atom (since the number of protons equals the number of electrons in a neutral state). However, the atomic number itself is not a direct measure of neutrons or energy levels, reinforcing the specificity and importance of this concept in atomic structure.