Using the letters A-I, write the formula of?

a)
(D is a noble gas because it has the greatest ionization energy across a period.)

The answer: A and I
(They belong to Group 15, or Group V.)

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b)
i.
C₂
(C is a halogen.)

ii.
D
(D is a noble gas.)

iii.
G₂O₃
(G belongs to Group III.)

iv.
HH₄
(The first H stands for element H which belong to Group IV/Group 14. The second H stands for hydrogen.)