Which one of the following elements is most likely to form a 2+ ion? A. calcium
ID: 532492 • Letter: W
Question
Which one of the following elements is most likely to form a 2+ ion? A. calcium B. carbon C. fluorine D. oxygen E. sodium An iron (li) ion has: A. 24 electrons and a charge of 2+ B. 24 electrons and a charge of 2^- C. 26 electrons and a charge of 2^+ D. 28 electrons and a charge of 2^+ E. 28 electrons and a charge of 2^- What are the two different ions present in the compound CaS? A. Ca^+, S^- B. Ca^-2, S^2+ C. Ca^+, S^+ D. Ca^2-, S^2- E. Ca, S What are the two different ions ions present in the compound FeCl_3? A. Fe^2+, Cl_3^- B. Fe^3-, Cl^3 C. Fe^+, Cl^- D. Fe^2+, Cl^- E. Fe^-, Cl^- What is the empirical formula for C_6H_14 O? A. C_4H_14O B. C_2H_2O C. C_2H_7 O D. C_12H_28 O_2 E. CHO What is the ion ClO_4^- named? A. chloride ion B. chlorite ion C. hypochlorite ion D. perchlorite ion E. perchlorate ionExplanation / Answer
20. Here, we have to consider the electronic configuration of the elements. The maximum electrons present in the shells are given in the order 2,8,8,18, etc starting from the first shell. So, we have:
Ca(20) = 2,8,8,2 C(6) = 2,4 F(9) = 2,7 O(8) = 2,6 Na(11) = 2,8,1
Completely filled outermost shell is the criteria for stability of the element as this is the configuration of the highly stable inert gases. From the above we observe that Ca can donate 2 electrons so that its outermost shell is completely filled. C can either donate or accept 4 electrons. F needs 1 electron to completely fill its outermost shell. O needs 2 electrons and Na can donate 1 electron. Hence, we can conclude that Ca can donate 2 electrons to form Ca2+.
21) Iron has atomic number = 26. Its electronic configuration is 1s22s22p63s23p63d64s2. Here iron can easily loose its 4s electrons and become Fe2+. So, the correct answer is (A) 24 electrons and charge of 2+.
22) CaS contains calcium and sulphur and we know from the electronic configuration of Ca that calcium can easily loose 2 electrons to form Ca2+. Also, S has atomic number 16(2,8,6) so, it can readily accept 2 electrons. Hence, the correct answer is (D) Ca2+ and S2-.
23) In FeCl3 we have two elements i.e. Fe and Cl. Chlorine has atomic number 17(2,8,7) so, it needs 1 electron to complete its inert gas configuration. Fe can easily loose 2 electrons from its 4s orbital to form Fe2+. Here, Fe can also loose one more electron from its 3d-orbital so that the 3d-orbital will be exactly half-filled (i.e. 3d6 to 3d5). Therefore formation of Fe3+ is highly feasible. So, if we work out the math, we observe that Fe will loose 3 electrons and three Cl atoms will receive one electron each. Hence, the ions which are present in FeCl3 are Fe3+ and Cl-. The correct answer is (D).
24) Empirical formula of a chemical compound is the simplest positive integer ratio of atoms present in a compound. Here, we are given C6H14O so the simplest positive integer ratio of atoms present will be C6H14O itself. The correct answer is (A).
25) ClO4- ion has the name perchlorate ion. The correct answer is (E).
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