Question

period and group numbers of first 20 elements??
plz answers fast....
urgently needed....
no useless answers plz...​

Answer 1

Answer:

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Explanation:

Hydrogen #1. period 1.

Helium #2. period 1, group 18.

Lithium #3. period 2, group 1.

Beryllium #4. period 2, group 2.

Boron #5. period 2, group 13.

Carbon #6. period 2, group 14.

Nitrogen #7. period 2, group 15.

Oxygen #8. period 2, group 16.

Answer 2

Answer:

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