valence electron
outer shell electron that is associated with an atom, and that can participate in the formation of a chemical bond if the outer shell is not closed
en-GB/ˈvæləns ɛlɛktɹɒn/
en-US/ˈveɪləns ɪˈlɛktɹɑn/
outer shell electron that is associated with an atom, and that can participate in the formation of a chemical bond if the outer shell is not closed