The significance of an outer electron is that it is the (only) electron that can interact with other electrons, rendering it extremely valuable.
no it only has 1 electron in the outer shell
An electron is not an element.
The key to "happiness" for an atom is a full outer electron shell. (The outer electron shell is called the valence shell.) There are two conditions that cause a shell not to be full. Either it has only an electron or two (or three) in the outer electron shell or it's short an electron or two in that outer shell. The direct answer to the question is that if an element is chemically active, its outer electron shell is incomplete or is not full.
Sodium has one outer ring electron, and chlorine has seven outer ring electrons. Sodium tends to lose its outer electron, while chlorine tends to gain an extra electron to achieve a stable electron configuration.
Lithium and potassium are both alkali metals. Thus their outermost orbitals are filled up to s1. So, that shows us that they both have only one outer level electron each.
Chlorine will tend to gain one electron to achieve a stable electron configuration with a full outer shell. This results in the formation of the chloride ion, which has a full outer shell of electrons.
Sodium has one electron in its outer ring.
Alkali metals have 1 electron in their outer shell.
The outer electron shells of halogens have seven electrons, making them one electron short of a full outer shell. This makes halogens highly reactive as they tend to gain an electron to achieve a stable electron configuration. Halogens are located in Group 17 of the periodic table.
Sodium has one electron in its outer shell, so it tends to lose that electron to achieve a full outer shell. This makes sodium more stable as it follows the octet rule by having a complete outer electron shell with eight electrons.
Bromine has 7 electrons in its outer shell and needs to gain one electron to have a full outer shell and become an ion. It will gain this electron from an atom that has one electron in its outer shell such as Lithium or Sodium.
Nitrogen has 5 electrons in its outer shell, so there are 3 electron pairs in the outer shell of nitrogen.