Answer:
I'll go in order from top to bottom (The boldened words are the ones that are supposed to go in the blanks.)
A chemical formula tells us what type(s) of atoms are in a substance and in what amount. Each atom belongs to a specific element and is shown with a symbol, which is listed on the periodic table.
The H stands for Hydrogen; The O stands for Oxygen
The subscript 2 after the H means that there are two atoms of hydrogen.
The absence of a subscript after the ) means that there's only one atoms of oxygen.
The chemical formula tells us that the (compound/chemical) of water has two hydrogen atoms and one oxygen atom.
Q1: 2 nitrogen atoms and 1 oxygen atom
Q2: KCl (potassium chloride)
Q3: The white spheres indicate hydrogen and the red sphere indicates oxygen.
Like chemical formulas, images show the composition and structure of atoms in substances.
Images also show the structural bonds that connect a substance's atoms.