Writing Chemical Formulas

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Nicole Jakiel 4F
Posts: 32
Joined: Fri Sep 28, 2018 12:28 am

Writing Chemical Formulas

Postby Nicole Jakiel 4F » Fri Nov 02, 2018 6:18 pm

Can anyone explain why the chemical formula for aluminum hydride is AlH3?

David S
Posts: 54
Joined: Fri Sep 28, 2018 12:15 am

Re: Writing Chemical Formulas

Postby David S » Fri Nov 02, 2018 7:42 pm

The nomenclature suggests that hydrogen is acting more like an anion in this case (hence the -ide ending in hydride) because Hydrogen is more electronegative than aluminum (2.1 vs 1.5).
That being said, Aluminum is acting like a +3 cation in this case. Since each hydrogen is basically a -1, we need three of them to balance out aluminum's +3 charge; Aluminum had three electrons to give, three hydrogens each had one electron to take.

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