Question

DJ SL Bodfre E) none of the above 48. How many valence electrons are in a chlorine atom? A) 1 B) 7 C) 17 D) 10 E) none of the above 49. Which of the following elements has the electron configuration of 3s 3p in its outermost shell A) Si B) Al C) CI D) S E) none of the above 50. If the electron configuration of a ground state sodium atom is 1s 2s2p635), the electron configura sodium cation (Na+) would be: A) 18²2s 2p B) 1s 2s 2p 3s' C) 1s 2s 2p 3s!

Answer 1

48. Chlorine has atomic number 17

So its electronic configuration is $1s^22s^22p^63s^23p^5$

As there are 2 electrons in 3s subshell and 5 electrons in 3p subshell i.e. a total of 7 electrons in shell 3 (outermost shell), so Chlorine atom has 7 valence electrons. So option (B) is the correct answer.

49. A) Si has atomic number 14, so its electronic configuration is $1s^22s^22p^63s^23p^2$ . So this is not the correct answer.

B) Al has atomic number 13, so its electronic configuration is $1s^22s^22p^63s^23p^1$ . So this is not the correct answer.

C) Cl has atomic number 17, so its electronic configuration is $1s^22s^22p^63s^23p^5$ . So this is not the correct answer.

D) S has atomic number 16, so its electronic configuration is $1s^22s^22p^63s^23p^4$ . So right answer is option (D).

E) As correct answer is option (D) so option E is also incorrect.

50. Sodium cation (Na⁺) is formed by loss of one electron from the outermost shell because it has a +1 charge. Loss of one electron (which carries a -1 charge) from a neutral atom means it now has a total of 10 electrons and 11 protons (each carrying a +1 charge). So electronic configuration of Na⁺ is $1s^22s^22p^6$ which is option (A).