Explain why reactivity trends are different for metals vs nonmetals in terms of ionization energy, atomic energy, and electron affinity

Asample of radium-226 will decay 1/4 of its original amount after 3200years. what is the half-life of radium-226?

What is the mass of 0.46 mil of mgcl2

Consider hydrogen in an excited state n = 5n=5 that emits photons to reach the ground state. there are various possible transitions other than straight to the ground state that can occur; for example, it can drop to the n = 3n=3 state followed by the n = 3n=3 to the ground state transition. which of the possible transitions will result in the emission of a photon in the visible region?