Why isn't the mass of the electron included in the mass of an atom on the periodic table?

According to the vsepr theory what is the shape of a molecule that has a central atom valence three other items with no lone pairs of electrons

For each of the compounds below, show that the charges on the ions add up to zero. a. kbr b. cao c. li(2)o d. cacl(2) e. alcl(3)

The density of benzene at 15 °c is 0.8787 g/ml. calculate the mass of 0.1500 l of benzene at this temperature. enter your answer in terms of grams