Which of the following explains why elements in column 17 (the halogens) are very reactive?
Their atoms contain three energy levels.
Their atoms need only one electron to complete their outer energy level.
Their atoms have large masses.
Their atoms contain the same number of protons as electrons.
Their atoms contain three energy levels.
Their atoms need only one electron to complete their outer energy level.
Their atoms have large masses.
Their atoms contain the same number of protons as electrons.