Sunday Puzzle: -IUM Pandemonium

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Sunday Puzzle NPR

NPR On air challenge

The suffix -IUM ends the names of most metallic elements. But it’s also the ending of other words that aren’t elements. Answer these clues for them.
Ex. Boredom  –>  TEDIUM

1. Size between small and large

2. Fish tank

3. Skull

4. Platform for a speaker

5. Large hall for physical exercise

6. Sun room

7. Building in which the stars of the night sky