Question

a chemist made the table below to record some atomic properties of four elements.
based on the information in the table, which conclusion about the chemical reactivity of these elements is valid?
a krypton is the least reactive because it has 8 electrons in the outer shell.
b beryllium is the most reactive because it has 2 electrons in the outer shell.
c sulfur is the most reactive because it has the same number of electrons, protons, and neutrons.
d oxygen is the most reactive because it has the same number of protons and neutrons.

Explanation:

• Krypton (Kr): In the periodic table, noble gases (like Kr) with 8 electrons in their outer shell (octet configuration) are very stable and have low reactivity.
• Beryllium (Be): Having 2 electrons in the outer shell (but it's in the second period, and its reactivity is not the highest among these as it has a relatively stable electron configuration compared to some other metals not in the table).
• Sulfur (S): Just having the same number of protons and neutrons (which gives mass number, but this doesn't directly relate to being the most reactive. Its reactivity is more related to its electron - shell configuration for bonding, but it's not the most reactive here).
• Oxygen (O): Having the same number of protons and neutrons (again, mass - number related, not reactivity. Its reactivity is due to its electron - shell configuration seeking to gain electrons, but it's not the case that this equality makes it the most reactive).

Answer:

A. Krypton is the least reactive because it has 8 electrons in the outer shell