Question

For which of the following elements its group number in short form of modern periodic table is no
equal to its valency?
1) Se
4) Fr
3) Sn
2) Xe

please help me
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Answer 1

Answer:

SE

Explanation:

becz it have mass with morden periodic table

Answer 2

Answer:

1) Se - Selenium

Explanation:

Selenium is in group VI of old short form of periodic table. Valency of Se is 2 which is not the group  number.