If you have .5L of N2 how many grams do you have?

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!

What is the wavelength of a wave with a velocity of 50 m/s and a frequency of 5hz a 250 m b 0.1 m c 10m d 0.01 m

If one fission reaction of a uranium-235 atom produced two neutrons, how many neutrons would be released if the chain reaction occurred three more times?