Cambridge Secondary (7-9). Stage 9. Science. Learner's Book - Unit 2: Properties of materials - Question 45

Group 8 data: helium (He): atomic number 2, electronic structure 2, mass number 4, melting point −270 °C, boiling point −269 °C; neon (Ne): 10, 2,8, 20, −249 °C, −246 °C; argon (Ar): 18, 2,8,8, 40, −189 °C, −186 °C.

Suggest why this group is called Group 8.