Humber Admissions Practice Test

With respect to electron configuration, what is the significance of the row number in the periodic table?

1. It indicates the number of protons

2. It indicates the number of shells

3. It indicates the number of neutrons

4. It indicates the atomic number

The correct answer is: It indicates the number of shells

The correct answer highlights the significance of the row number in the periodic table as it indicates the number of electron shells that an element has. Each row, or period, corresponds to a distinct energy level that can hold electrons. For example, elements in the first row (period 1) have one electron shell, while elements in the second row (period 2) have two electron shells. This information is crucial for understanding how electrons are arranged in atoms, affecting their chemical properties and reactivity. In contrast, the other choices do not accurately reflect the significance of the row number. The number of protons is determined by the atomic number, which is a unique identifier for each element rather than a characteristic defined by its row in the table. Similarly, while neutrons contribute to an element's atomic mass, they are not indicated by the row number. Finally, the atomic number specifically refers to the number of protons in the nucleus, which is distinct from the information conveyed by the position of an element in a row of the periodic table.