What Tells the Atoms how to Behave?

What tells the atoms to behave differently than atoms of another element? also how do they come to know that they are the atoms of a particular element and what color are the electrons protons neutrons?
- saumya (age 14)
dehradun uttarakhand india

First a conceptual point: atoms are elements themselves, that is whatever chemical property you observe is due to some interactions/properties of these. Therefore they do not need to know about their context, they are what they are and identical atoms are indistinguishable. The difference between neutral atoms of different elements is mainly the number of protons (=number of electrons). Each and every element has a different number of protons within the nucleus + some neutrons, whose number may vary (aka isotopes). This means they will have a different Coulombic potentials, meaning the electronic energy levels will be different. This difference make their behavior different, such as tendency to bond with other chemicals or undergo excitation.

Now, color is not some concrete substance, similar to the historical caloric concept. It is a property that we attribute to the dominant wavelength emitted from an object. Under white light, we call something red if it reflects/transmits red light more compared to the others (say blue), which is equialent to blue being absorbed or scattered significantly more. The color of the objects around are dominantly determined by the electronic energy levels in the constituent atoms or molecules: the wavelengths matching one of the excitation energy gaps tend to be absorbed. For free electrons, neutrons and protons no such energy level pattern is obvious. Due to this contious spectrum, they would absorb and emit photons at all wavelengths to a degree, so I think we could maybe call their clouds white.

Tunc

(published on 07/19/2015)