What is atomic number :
**Core Concept:** The atomic number refers to the number of protons in an element's nucleus, which determines its position in the Periodic Table and its chemical properties. Each element has a unique atomic number, with hydrogen having an atomic number of 1, helium 2, and so on.
**Why the Correct Answer is Right:** The correct answer, **D (Z=93)**, represents the atomic number for radon, a radioactive gas element with 93 protons in its nucleus. The atomic number corresponds to the position of an element in the Periodic Table, reflecting the number of protons in the nucleus.
**Why Each Wrong Option is Incorrect:**
A. Atomic number refers to the number of protons, not neutrons. Option A (Z=35) is discussing the atomic mass instead.
B. Atomic number is determined by protons, not electrons. Option B (Z=15) refers to the number of electrons, which is different from the atomic number.
C. Atomic number is unique to each element, not based on the number of electrons. Option C (Z=8) is incorrect because it refers to the number of electrons, which is different from the atomic number.
**Why the Correct Answer is Right:** The correct answer, **D (Z=93)**, represents the atomic number for radon, a radioactive gas element with 93 protons in its nucleus. The atomic number corresponds to the position of an element in the Periodic Table, reflecting the number of protons in the nucleus.
**Clinical Pearl:** Understanding atomic number helps medical professionals determine an element's position in the Periodic Table, which is crucial for identifying elements and their chemical properties, essential in various medical fields, including chemistry, radiology, and nuclear medicine.