Question

Explain how the image is formed by thin convex lens and derive 21

1 2

11 1 1 ( 1)

R R

n

u v

é ù

- += - + ê ú ë û​

Answer 1

Thus, helium is the smallest element, and francium is the largest. From top to bottom in a group, orbitals corresponding to higher values of the principal quantum number (n) are being added, which are on average further away from the nucleus, thus causing the size of the atom to increase.