Calculate the number of atoms

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?

The chemical bond connecting one nucleotide with the next one along the nucleic acid chain is called a

Which of the following units is not an official si unit