What must happen for an electron to move to a higher energy level?
o
the electron must gain energy
o
the electron must transfer energy to another electron.
the electron must release energy through fission.
o
the electron must collide with the nucleus.

The electron must gain energy.

Explanation:

For a electron to be promoted from one energy level to a higher energy level it has to absorb energy. If the electron decay back to the initial energy level will emit a photon with the a energy equal of the difference between the two energetic levels.

fire could start, buildings collapsing, and ash falling from the sky.

explanation:

this is because the buildings or plants could catch on fire and the buildings would most likely collapse. lastly ash would fall because all the burning would cause ash to fall from the sky.

hope this .

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements