Determine the empirical and molecular formula for a compound containing 26.1 % carbon, 4.3% hydrogen, and 69.6% oxygen. Molar Mass = 138 g/mol.

Sally is making a model of a magnesium atom with an atomic mass number of 24 for her chemistry class. she has foam balls for the protons, neutrons, and electrons. she has added 6 neutrons to her model so far. how many more neutrons does she need to add to complete her neutral atom of magnesium?

Is 343 in the sequence -5, -2, 1, 4, 7

What is the empirical formula of a compound that is 50.7% antimony and 49.3% selenium ?