How many valence electrons does a helium atom have?

Which of the following shapes would represent a molecule with two bonded atoms and 3 lone pairs on only one of them , trigonal planar , bent , trigonal pyramidal , linear

If 16.00g of hydrogen gas reacts with 126.73g of oxygen, how many grams of water are yielded? (both reactants are completely consumed in the reaction.)

Determine the ph of 0.10 m nh3 solution. nh3 is a weak base with a kb equal to 1.8 x 10-5 round answer to nearest whole number.