Light/thermal. Charges move back and forth which move at the speed of light
A large number in front of a compound designates how many units there are of that compound. Parentheses can be used to designate a special structure, where other molecules are attached to the larger, complex molecule.
Answer:
32.7 kilograms of aluminium oxide will be produced.
Explanation:

Mass of aluminum = 17.3 kg = 17300 g (1 kg = 1000 g )
Moles of aluminium = 
According to reaction, 2 moles of aluminum gives 1 mole of aluminum oxide,then 640.74 moles of aluminum will give:
of aluminum oxide
Mass of 320.37 moles of aluminum oxides:
320.37 mol × 102 g/mol = 32,677.74 g = 32.67774 kg ≈ 32.7 kg
32.7 kilograms of aluminium oxide will be produced.
Explanation:
first one because absolute dating is a thing for rock layers