Question

3. Which element has
(a) two shells, both of which are completely filled with electrons?
(b) the electronic configuration 2, 8, 2?
(c) a total of three shells, with four electrons in its valence shell?
(d) a total of two shells, with three electrons in its valence shell?
(e) twice as many electrons in its second shell as in its first shell?​

Answer 1

1. 2,8
2. magnesium
3. silicone
4. aluminium

.......

I hope this helps u

mark me brainlist

Answer 2

$\LARGE\underline{\purple{\sf{Required\:answer:-}}}$

(a) Neon is the element with two shells completely filled with electrons . As it has 10 electrons , the configuration becomes 2 , 8.

(b) The given configurations tells us that the atom has 2 valence electrons and 12 electrons . The element with 12 electrons and 2 valence electrons is Magnesium .

(c) Given that the atom has total three shells (K , L , M) and four electrons in the valence shell. Valence shell is M (as per given information) and has 4 electrons . In the before two shells should be completely filled with electrons. K shell accommodates 2 electrons and M shell accomodates 8 electrons (Their maximum capacity). So , The configuration becomes 2, 8, 4 . The element with 14 electrons and 4 valence electrons is Silicon .

(d) Given that the atom has total two shells (K , L) and three electrons in the valence shell. Valence shell is L (as per given information) and has 3 electrons . In the before one shell hould be completely filled with electrons. K shell accommodates 2 electrons (It's maximum capacity). So , The configuration becomes 2, 3 . The element with 5 electrons and 3 valence electrons is Boron .

(e) The maximum capacity of first shell is 2 . Twice the electrons present in first shell is the numbef of electrons present in second shell (given) . Twice the number of electrons in first is 4 . So , Second shell has 4 electrons and now configuration becomes 2 , 4 . The element with 6 electrons and 4 valence electrons is Carbon .