Which group of the periodic table of elements forms only 1+ ions?

Answer is group 1A. Why?

So if the question asked which group forms only 2+ ions, the answer would be group 2 because it has 2 outermost electrons? And we know it has 2 outermost electrons based on the group number?

There is only one outermost electron.

exactly right.

The group of elements in the periodic table that forms only 1+ ions is Group 1A, also known as the alkali metals. These elements include hydrogen (H), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

To understand why these elements only form 1+ ions, we need to look at their electron configurations. The elements in Group 1A all have one valence electron, meaning that their outermost energy level contains only one electron. Valence electrons are the electrons involved in chemical reactions and are responsible for the formation of ions.

In order to achieve a stable electron configuration, these elements can easily lose their one valence electron. By losing an electron, they attain a stable configuration with a full outermost energy level, similar to the noble gases. Since losing one electron leaves them with a net positive charge, they form 1+ ions. For example, sodium has the electron configuration [Ne] 3s1. By losing its single valence electron, it forms the Na+ ion with a stable electron configuration of [Ne].

This trend holds true for the other elements in Group 1A as well. They all have one valence electron, and by losing it, they form 1+ ions. It's important to note that the elements in this group have a strong tendency to lose their valence electron, making them highly reactive and easily forming positive ions in chemical reactions.