Using a periodic table, answer the following question: Which series of elements have the same number of valence electrons?
A. Sn, Pb, F, I
B. Ca, Sr, Cu, Ag
C. Na, Mg, Si, B
D. N, P, Sb, Bi

How does the atmosphere to make earth livable? check all that apply. causes the seasons contains oxygen provides warmth creates important nutrients blocks harmful energy from the sun plz like !

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?

What is the wavelength of a 3*10^12 hz infrared wave a 3*10^20m b 1* 10^4m c 3*10^-3m d 1*10^-4 m