24 Which of the following ions have the same ground state electron configuration

Question

24 Which of the following ions have the same ground state electron configuration: s N' Mg2 and a. N3- and Mg 2+ b. s2- ,N3-, and Br c, S2- and Br d. Mg and Br e, s N3 ,Mg and Br Which of the following has the same total) number of electrons as Arm a. Na Ca c. o2- none 26. What 2+ ion has the following ground state electron configuration? Sp d. sn e, None a. cd b. sr c. 27. The ground-state electron configuration of a Mn ion is 1s22s 2p63s23p 3ds Therefore, Mn is a. paramagnetic with five unpaired electron b. diamagnetic. unpaired electron. c, paramagnetic with one d. paramagnetic with three unpaired electrons. e, paramagnetic with two unpaired electrons. 28. An atom of which of the following elements has the smallest atomic radius? a, b. K c. Ca d. Si e. 29. An atom of which of the following elements has the largest atomic radius? C a. Ge b. Sn C. Si d. Pb e. ANSWER:

Explanation / Answer

Solution:- (24) To have the same ground state electron configuration the number of electrons must be same that means the species must be isoelectronic.

atomic number of S is 16 and there is -2 charge on it so total number of electrons would be 18.

Atomic number of N is 7 and ther charge on it is -3. so total electrons would be 10.

Atomic number of Mg is 12 and it has +2 charge so total electrons would be 10.

Atomic number of Br is 35 and the given charge is -1 so total electrons would be 36.

Comparing all of there N3- and Mg2+ has equal number of electrons so their ground state electron configurations would also be same.

So, the correct choice is a. N3- and Mg2+

(25) Atomic number of Na is 11 and the given charge is +1 so the total electrons would be 10.

Atomic number of Ca is 20 and it has +2 charge so total electrons would be 18.

Atomic number of Ga is 31 and there is +3 charge on it so the total electrons would be 28.

Atomic number of O is 8 and it has -2 charge so total electrons would be 10.

Atomic number of Ar is 18, that means it has 18 electrons in total.

The only correct choice is b, Ca2+ since it has 18 electrons.

(26) Atomic number of Kr is 36. So, the total number of electrons for the given electron configuration is 36 + 10 + 2 = 48

(36 electrons for [Kr], 10 electrons for 4d and 2 electrons for 5s).

Atomic number of Cd is 48 and there is +2 charge so the total electrons would be 46.

atomic number of Sr is 38 and it has +2 charge so the total electrons would be 36.

atomic number of Zn is 30 and it has +2 charge so the total electrons would be 28.

atomic number of Sn is 50 and the given charge is +2 so the total electrons would be 48 which is exatly same as for the given electron configuration.

So, the correct choice is d. Sn2+.

(27) From given electron configuration all the subshells are completely filled except 3d. as shown in question number 26, d subshell could hold maximum 10 electrons. It is exactly half filled when it has 5 electrons. Pairing of electrons starts from the 6th electron.

Since, Mn2+ electron configuration has only 5 electrons in 3d, all these 5 electrons are unpaired and the element of ion is paramagnetic if it has unpaired electrons. So, the correct choice is a. paramagnetic with five unpaired electrons.

(28) The general trend for atomic radius is, it decreases left to right and increases top to bottom. It means on moving left to right in the period, atomic radius decreases and increases on moving top to bottom in the group.

Si, P and Cl are th elements of 3rd period where as K and Ca are the elements of 4th period. So, from here, atomic radius of K and Ca would be larger as compared to 3rd period elements Si, P and Cl.

in Si, P and Cl, it is Cl which is on the right most side in 3rd period so the atomic radius would be smallest for Cl. Hence the correct choice is a. Cl

(29) C, Si, Sn and Pb are the elements of same group and we know that atomic radius increases on moving down in a group. So, in these four the larger radius is for Pb.

Now, if we compare Pb and Ge then Ge is in 4th period where as Pb is in 6th period. Atomic radius also increases on going from one period to another. So, the largest atomic radius would be for Pb. The correct choice is d. Pb.

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