Why does the reactivity of non-metals increase moving left to right on the periodic table?
a. The atomic mass of each element’s atoms increases.
b. Atoms of elements are closer to filling their valence shell with electrons.
c. Atoms of elements more easily let go of their valence electrons.
d. The valence shells of each element’s atoms get larger.
The correct Answer and Explanation is:
The correct answer is b. Atoms of elements are closer to filling their valence shell with electrons.
Explanation
The reactivity of non-metals increases from left to right across the periodic table primarily due to the effective increase in electronegativity and the desire of these elements to complete their valence electron shell. Non-metals, such as oxygen, nitrogen, and fluorine, typically have high electronegativities, which is the tendency of an atom to attract electrons. As you move from left to right across a period, the atomic number increases, resulting in a greater positive charge in the nucleus. This greater positive charge attracts the electrons more strongly.
Non-metals have a tendency to gain electrons to achieve a stable electronic configuration, often resembling the nearest noble gas, which has a complete valence shell. For instance, the halogens (Group 17) are one of the most reactive groups of non-metals because they have seven valence electrons and need only one more to achieve a full octet. As you progress across the periodic table, elements gain more protons and consequently more electrons, making them more efficient at attracting additional electrons to fill their outer shell.
In contrast, non-metals on the left side of the periodic table, such as carbon and boron, have fewer valence electrons and thus are less eager to gain electrons compared to elements on the right side. This increasing tendency to gain electrons as you move to the right accounts for the enhanced reactivity of non-metals, particularly in their ability to form covalent bonds with other elements by sharing or gaining electrons.
Overall, the trend of increasing non-metal reactivity from left to right is a reflection of the increasing effective nuclear charge and the resulting affinity for additional electrons to complete the valence shell, making option b the correct choice.