Group 1 contains metals while group 18 contains noble gases.
So group 1 is different from group 18 as they both contains different types of atoms as group 1 contains metals while group 18 contains noble gases.
There is 1 valence shell electron in group 1 , they are highly reactive while valence shell of group 18 is fully filled and they are least reactive .
A loss of negatively-charged electrons corresponds to an increase in oxidation number, while a gain of electrons corresponds to a decrease in oxidation number. Therefore, the element or ion that is oxidized undergoes an increase in oxidation number.
Hope this helped
Yes because the stigma rises above the gas I think that’s is it
D.) He arranged elements by Atomic Masses
To me, I think the Earth was made around 6,000 years ago.