Describe how our lives would
be different if the lightbulb
had never been invented.

If the light bulb had never been invented, we would use natural sunlight as light during the day and fire or candles when we cannot see the sun. Since the light of candles is rather dim, most people would also sleep and wake up early, with the sun. The streets would be darker at night, even in urban areas.

Many other inventions that use the light bulb may not have been invented, or would be different. For example, our computer screens and television screens are forms of small light bulbs. Car headlights use light bulbs as well.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.