Which salt has the most stable bonds nacl kcl nh4cl and bacl2

Aroller coaster car is traveling down a track at 22 m/s. the car has a mass of 2000 kg. what is the kinetic energy of the car? a) 22,000 j b) 968,000 j c) 484,000 j d) 44,000 j

As changes in energy levels of electrons increase, the frequencies of atomic line spectra they emit

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!