How many valence electrons does alkali metals?

Iknow #2 is d. i just need to know why

Match the following items. 1. high-intensity bundle of energy being emitted from some decaying nuclei gamma ray 2. particle radiating from the nucleus of some atoms beta particle 3. negative particle identical to an electron but radiating from a decaying nucleus alpha particle

What is the maximum number of electrons that an atomic orbital can contain?