Which of the following species are isoelectronic? Select all that apply.
1) S^2-
2) Be^2+
3) Cl^-
4) K^+
5) Ca^2+
6) Se^2-
Answered below.
So far I have S^2-, Cl^-, K^+, and Ca^2+ instead the other two as the answer. Please tell me if I have these answers correct.
Isoelectronic species are those that have the same number of electrons. To determine which of the species are isoelectronic, we can compare the electron configurations of each one.
1) S^2-: The atomic number of sulfur is 16. Sulfur normally has 16 electrons, but since it has a charge of 2-, it gains 2 more electrons. Therefore, the electron configuration is 1s^22s^22p^63s^23p^6.
2) Be^2+: The atomic number of Beryllium is 4. Beryllium normally has 4 electrons, but it loses 2 electrons to form a 2+ charge. Therefore, the electron configuration is 1s^22s^2.
3) Cl^-: The atomic number of Chlorine is 17. Chlorine normally has 17 electrons, but since it has a charge of 1-, it gains 1 more electron. Therefore, the electron configuration is 1s^22s^22p^63s^23p^6.
4) K^+: The atomic number of Potassium is 19. Potassium normally has 19 electrons, but it loses 1 electron to form a 1+ charge. Therefore, the electron configuration is 1s^22s^22p^63s^23p^64s^1.
5) Ca^2+: The atomic number of Calcium is 20. Calcium normally has 20 electrons, but it loses 2 electrons to form a 2+ charge. Therefore, the electron configuration is 1s^22s^22p^63s^23p^64s^2.
6) Se^2-: The atomic number of Selenium is 34. Selenium normally has 34 electrons, but it gains 2 electrons to form a 2- charge. Therefore, the electron configuration is 1s^22s^22p^63s^23p^64s^23d^104p^6.
From comparing the electron configurations, we find that species 1) S^2- and 6) Se^2- are isoelectronic as they both have the configuration of 1s^22s^22p^63s^23p^6.
To determine which of the following species are isoelectronic, we need to compare their electron configurations. Isoelectronic species have the same number of electrons.
1) S^2-: The sulfur ion has gained two electrons, so its electron configuration is 1s^2 2s^2 2p^6 3s^2 3p^6. It has 18 electrons.
2) Be^2+: The beryllium ion has lost two electrons, so its electron configuration is 1s^2 2s^2. It has 4 electrons.
3) Cl^-: The chloride ion has gained one electron, so its electron configuration is 1s^2 2s^2 2p^6 3s^2 3p^6. It has 18 electrons.
4) K^+: The potassium ion has lost one electron, so its electron configuration is 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1. It has 19 electrons.
5) Ca^2+: The calcium ion has lost two electrons, so its electron configuration is 1s^2 2s^2 2p^6 3s^2 3p^6 4s^0. It has 18 electrons.
6) Se^2-: The selenium ion has gained two electrons, so its electron configuration is 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^2 4d^10 5p^6. It has 36 electrons.
Comparing the electron configurations, we can see that S^2- and Cl^- have the same number of electrons (18), so they are isoelectronic.
Therefore, the species that are isoelectronic are:
1) S^2-
3) Cl^-