Why is helium in group 18 on the periodic table though it only has 2 valence electrons?

Look at the spectrums of a star moving towards earth and a motionless star. which of these is a correct inference that can be draw from the observation of the two spectrums? (2 points) the spectrum of a motionless star is difficult to be viewed separately using oridinary telescopes. the spectrum of a motionless star is identical to the spectrum of a star which moves towards earth. the spectrum of a star shifts towards the red region when the star moves towards earth. the spectrum of a star shifts towards the blue region when the star moves towards earth.

What substance has a mass of 9.5g and volume of 2.1cm^3

Is 9 correct? and can someone me with 10? it’s due tomorrow, you