The bigger gray circle represents the oxygen atom in the water molecule, and the smaller black circles represent the hydrogen atoms.
The correct answer is option 4 "atoms".
The diagram of the water molecule shows two smaller black circles and one larger gray circle. The larger gray circle represents the oxygen atom, and the smaller black circles represent the hydrogen atoms.
An atom is the smallest unit of matter that can still retain the properties of a chemical element. Atoms are made up of even smaller particles called protons, neutrons, and electrons. Protons and neutrons are found in the nucleus of the atom, while electrons orbit around the nucleus.
The oxygen atom in the water molecule has eight protons and eight neutrons in its nucleus. It also has eight electrons orbiting around the nucleus. The two hydrogen atoms each have one proton and one neutron in their nuclei. They also have one electron each orbiting around the nucleus.
Atoms are bonded together to form molecules by sharing or transferring electrons. In the water molecule, the oxygen atom shares one of its electrons with each of the hydrogen atoms. This forms two covalent bonds between the oxygen atom and the two hydrogen atoms.
The covalent bonds between the oxygen atom and the hydrogen atoms are represented by the lines in the diagram of the water molecule. The larger gray circle representing the oxygen atom is connected to the two smaller black circles representing the hydrogen atoms by two lines.
Conclusion:
The bigger gray circle in the diagram of the water molecule represents the oxygen atom, and the smaller black circles represent the hydrogen atoms. The lines connecting the oxygen atom to the hydrogen atoms represent the covalent bonds between them.