What trend in atomic radius do you see as you go down a group on the periodic table

What is the amount of energy for a photon that has a 125 cm wavelength

An unknown substance is a white solid at room temperature and has a melting point of 78 °c. which of the following substances is most likely to be the identity of the unknown sample? a. naphthalene, a molecular solid with the formula c10h8 b. silica, a network solid held together by covalent bonds with the formula sio2 c. calcium chloride, an ionic compound with the formula cacl2 d. water, an molecular compound with the formula h2o

What is the best describtion of the side of the moon that faces earth?