The atomic structure of an atom is well explained experimentally by different experiments like Rutherford's experiment etc
Based on these experiments it was determined that the atoms contains a central part known as nucleus which contains the positively charged sub atomic particles protons and neutral sub atomic particles neutron.
There is empty space around the nucleus in which negatively charged subatomic particles are found known as electrons.
So answers are
a) protons
b) neutrons
c) electrons
There are 4 oxygens in the compound
The most accurate means of determining the purity of a substance is through the use of analytical methods. These methods, widely used in different industries, mostly involve chemical analysis, which can pinpoint the presence, identity and amount of impurities in the sample. The most simple chemical methods include gravimetry and titration. There are also the more advanced light-based or spectroscopic methods, such as UV-VIS spectroscopy, nuclear magnetic resonance and infrared spectroscopy. Chromatographic methods, such as gas chromatography and liquid chromatography, can also be used. Other methods used in testing the purity include mass spectroscopy, capillary electrophoresis, optical rotation and particle size analysis.
-basically nerdy talk for using machines controlling chemicals or other atoms to pinpoint any impurities