Identify the elements X and Y using the ionisation energy values given below :
1st ionization energy (kJ/mol) 2nd ionization energy (kJ/mol) X 495 4563 Y 731 1450
| 1st ionization energy (kJ/mol) | 2nd ionization energy (kJ/mol) | |
| X | 495 | 4563 |
| Y | 731 | 1450 |
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- X = F; Y = Mg
- X = Mg; Y = F
- X = Na; Y = Mg
- X = Mg; Y = Na
The Correct Option is C
Solution and Explanation
For Y: IE1 = 731 and IE2 = 1450, a moderate rise, so two valence electrons are present; this matches Mg (IE1 = 737, IE2 = 1450).
F has IE1 = 1681, far too high for either.
Answer: (3) X = Na; Y = Mg
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