Verified Answer :

  • The atomic number is the count of protons in an atom's nucleus.
  • Option (a) represents the atomic mass of chlorine, while (b) and (d) are associated with sulfur.
  • Chlorine is the element with 17 protons.
  • The correct atomic number of chlorine is \(\boxed{17}\).

Explanation

  1. Definition and Problem Analysis

The atomic number of an element is defined as the number of protons in the nucleus of an atom of that element. Each chemical element is uniquely identified by its atomic number, which determines its position in the periodic table. We are asked to identify the atomic number of chlorine from the given choices: a) 35.45, b) 16, c) 17, and d) 32.

  1. Evaluation of Options

Examining the options provided:

  • 35.45: This is the average atomic mass of chlorine, not the atomic number.
  • 16: This is the atomic number of sulfur.
  • 17: This is the atomic number of chlorine.
  • 32: This is a common mass number for sulfur, not the atomic number of chlorine.

Chlorine is a halogen located in Group 17 of the periodic table, and it has an atomic number of 17, indicating that a chlorine atom contains 17 protons in its nucleus.

  1. Final Answer

Based on the evaluation, the atomic number of chlorine is 17, which corresponds to option c. Thus, the correct answer is 17.

Examples

In chemistry, knowing the atomic number is essential for understanding how atoms bond and react. For instance, because chlorine has an atomic number of \(17\), it has an electronic configuration of \(2, 8, 7\), meaning it needs one more electron to achieve a stable octet. This property explains why chlorine is highly reactive and readily forms ions like chloride (\(Cl^-\)) by gaining an electron from other elements, such as sodium, to form table salt (\(NaCl\)).

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