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Why melting point increases upto arsenic and decreases upto bismuth?

Dear student!

Due to increase in atomic size down the group, the last two elements Sb and Bi have tendency to forms covalent bonds which weakens the attraction among their atom and thus lowers the melting point.

So, when we come down the group at first the melting point increases till As but when we come down again the size of Sb increases and also for the Bi and so they have gradual decrease in m.pts. 

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it is so because the pairing of electrones start as we move towards bismuth 

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as the size of atom increases as we moce down the group, the attraction of the electros towards nucleus decreases and so the melting point gradually decreases!! :) :D

  • -10

 There is not a mjajor decrease in the melting points after arsenic! But there is some! The valence electrons of Sb and Bi are shielded by f-orbitals.. F-orbitals are poor shielders! So,the melting point decreases!

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