Halogens have ______ electrons in their outermost shells.

The correct answer is Seven.

 Key Points

• The halogens are a group in the periodic table that consists of five or six chemically related elements: fluorine, chlorine, bromine, iodine (I), and astatine.
  • Halogens have 7 electrons in their outermost shell.
  • The boiling points of halogens tend to move down the group due to the increasing strength of van der Waals forces as the size and relative atomic mass of the atoms increase.
  • Halogens are the only periodic table group containing elements in all three familiar states of matter (solid, liquid, and gas) at standard temperature and pressure.
  • Halogens are highly reactive, and they can be harmful or even fatal to biological organisms in sufficient quantities.
  • This reactivity is due to the high electronegativity and high effective nuclear charge.
  • Halogens can react with atoms of other elements to gain an electron.

Additional Information

• The elements of Group 2 include beryllium, magnesium, calcium, strontium, barium, and radium.
  • These elements with the exception of beryllium are commonly known as alkaline earth metals.
• These elements are called Alkaline Earth metals because of two reasons:
  • Their oxides exist in the earth’s crust and are very stable to heat. 
  • Their oxides and hydroxides show basic (alkaline) natures.
  • Beryllium fulfills the first criterion but not the second one since its oxides and hydroxides show amphoteric behavior, rather than alkaline.