Both aluminum and chlorine have known charges, which are +3 and -1 respectively. To make them cancel each other out in charge, you would need 3 chlorine and for one aluminum, therefore

would be correct
Is this multi choice or no?
Infrared (IR) spectroscopy uses infrared radiation to excite the molecules of a compound and generates an infrared spectrum of the energy absorbed by a molecule as a function of the frequency or wavelength of light
The answer is C. Isotopes.
Isotopes are defined as two substances that have the same number of protons and electrons, but a different number of neutrons, and therefore a different atomic mass. For example, carbon-12 and carbon-14 are isotopes of each other.
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