The half-life of 222rn is approximately 4 days. a sealed vessel is found to contain 1.5 mg of 222rn. how much radon would have been present 12 days before this measurement was taken?

The chart shows the bid provided by four contractors to complete a job. which contractor is the most cost-effective?

An atom with 7 protons, 6 neutrons, and 7 electrons has an atomic mass of amu. (enter a whole number.) numerical answers expected! answer for blank 1:

I'm learning about the periodic tables and what each subject's configuration is. for example, hydrogen is 1s^1, but i don't understand how you get that. can someone me understand how to figure out how to figure this out? sorry if the question makes no sense, but it would really a lot if you could me understand! you so much if you can!