Question 21

Elements in the same row are characterized by an increasing number of protons from left to right.

In the periodic table, elements are arranged in rows called periods, and as one moves from left to right across a period, the atomic number of the elements increases, which corresponds to an increasing number of protons.

A) an increasing number of neutrons from left to right.

This option is incorrect because while the number of neutrons can vary among isotopes of an element, the primary characteristic of elements in the same row is their increasing number of protons, not neutrons. The neutrons do not have a consistent pattern of increase across a period.

B) a decreasing number of neutrons from left to right.

This option is also incorrect for the same reasons as Option A. The number of neutrons does not consistently decrease from left to right across a row in the periodic table; rather, it varies depending on the specific isotopes of the elements.

C) an increasing number of protons from left to right.

This option is correct as it accurately describes the arrangement of elements in the periodic table. Each successive element in a row has one more proton than the previous element, which defines its atomic number and positions it within the periodic table.

D) a decreasing number of protons from left to right.

This option is incorrect because it contradicts the fundamental structure of the periodic table. As one moves from left to right, the number of protons does not decrease; it increases, which is essential for determining the properties and classification of elements.

Conclusion

The correct answer is C, as it captures the essential characteristic of the periodic table's structure, emphasizing that elements in the same row possess an increasing number of protons. All other options misrepresent or overlook this fundamental aspect, highlighting the importance of understanding atomic structure for comprehending the organization of the periodic table.