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why the number of elements in the first ...

why the number of elements in the first period is only `2`?

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It is because the `1 st` energy level can have only `1s` orbital which can have two electrons. When `n=1`,`l=0`.
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CENGAGE CHEMISTRY ENGLISH-APPENDIX - INORGANIC VOLUME 1-Exercise Short
  1. Give four characteristics of s-block elements.

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  2. Give four defects of Mandeleev's periodic table.

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  3. why the number of elements in the first period is only 2?

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  4. On the basis of their electronic configuration, explain why alkali met...

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  5. Why do the melting points decrease in going from NaF to Nal?

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  6. Why are group 1 elements called alkali metals ?

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  7. Give five characteristics of d-block elements.

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  8. (a) What was the basis of Mendeleev's Classification of elements ? (...

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  9. Why does the solubility of alkaline earth metal carbonates and sulphat...

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  10. why is melting point of LiCI lower than NaCI?

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  11. Arrange the following in increasing order: a. BeCO(3),BaCO(3),CaCO(3...

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  12. Which alkali metal carbonate is thermally unstable and why?

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  13. The element which has highest electron affinity ?

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  14. What is diagonal relationship?

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  15. Give four characteristics of f-block elements.

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  16. Why are electron affinities of noble gases zero? Arrange halogens in i...

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  17. Arrange the species in each group in order of increasing ionisation en...

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  18. State the factors which affect electronaffinity

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  19. Explain the term (a) screening effect

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  20. which has higher 1st ionisation energy B or Be and why?

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