These models show the electron structures of two different nonmetal elements.

Question

Element 1 at left has a purple circle at center with 2 concentric black lines around it. The first line has 2 small green balls on it. The second line has 8 small green balls on it. Element 2 at right has a purple center with 5 concentric circles around it, with the first circle innermost. The first circle has 2 small green balls on it, and the second circle has 8 small green balls on it. The third circle has 18 small green balls on it, and the fourth circle has 18 small green balls on it. The fifth circle has 6 small green balls on it.

Which element is likely more reactive, and why?

Element 1 is more reactive because it has fewer electron shells and is toward the top of its group on the periodic table.
Element 1 is more reactive because it has more electrons in its valence shell and is farther to the right on the periodic table.
Element 2 is more reactive because it does not have a valence shell close to the nucleus, so it will attract electrons.
Element 2 is more reactive because it does not have a full valence shell, so it will attract electrons.

Answer 1

To determine which element is likely more reactive, we need to analyze their electron structures based on their descriptions.

Element 1 has:

• 2 electron shells (2 electrons in the innermost shell and 8 electrons in the second shell). The outermost shell (valence shell) has 8 electrons, which means it is a noble gas configuration, indicating low reactivity.

Element 2 has:

• 5 electron shells (2 electrons in the innermost shell, 8 in the second, 18 in the third, 18 in the fourth, and 6 in the outermost shell). The outermost shell (valence shell) has 6 electrons, which means it is not full (the full valence shell would have 8 electrons), making it more likely to react in order to gain additional electrons.

Given that Element 2 does not have a full valence shell and is more likely to gain electrons to achieve stability (octet rule), it is indeed more reactive than Element 1.

Therefore, the correct reasoning is:

Element 2 is more reactive because it does not have a full valence shell, so it will attract electrons.