Atoms of elements in the same group have the same number of [blank] this is why they have similar chemical properties.
a. protons
b. neutrons
c. valence electrons

Light traveling in a medium with a refractive index 1.19 is incident on a plate of another medium with index of refraction 1.79. at what angle of incidence is the reflected light fully polarized?

You've already seen the value of 9.8 in this lesson. what's this value called? what quantity does it represent?

The particles that are found in the nucleus of an atom are