2)Why is a large mass of uranium-235 needed for a chain reaction?1)Below are shell diagrams for four elementsUnder each indicate the number of valence electrons each element contains B2 circles, 3 dots on the outside circle, 2 on the 1 St and one in light colored one inn the middleC2 circles, 8 on the outside, 2 on the 1st, one light colored in the middleD3 circles, 3 on the 3rd circle, 8 on the 2nd, 2 on the 1St, one light colored one in the middleFBased on the number of their valence electrons which two elements belong to the the same groupYes i have done these and i got them wrongPlz help
