Question

Prepare a list of first 20 elements and write their atomic number ,mass number ,atomic mass, electronic configuration and valency.

Answer 1

hi bubby,

An element with electronic configuration 2,8 will have an atomic number 10.

Therefore, distribution of electrons in its sub shells is as follows.

                1s^{2}2s^{2}2p^{6}

Thus, this element has completely filled sub shells and hence, it belongs to group 18 which is also known as noble gas group.

Hence, we will place this element on the extreme right side below the helium atom. This element is neon.

Answer 2

Answer:

Explanation:I have uploaded a picture please see it

Thanks