In the sentence, "Each element of matter has distinct properties and a distinct atomic structure," what does the word structure mean?
Each element has a so-called nucleus which possesses all the positive charge and MOST of the mass of the atom. The number of positively charged particles in the nucleus,
Neutrons, massive NEUTRALLY charged nuclear particles also reside in the nucleus. (In other words the nucleus consists of these massive particles). Different numbers of neutrons in the nucleus give rise to the existence of isotopes, i.e.
Electrons, fundamental negatively charged particles of negligible mass, are conceived to orbit around the nucleus in strict geometries (defined by a wave function) and with quantized levels of energy (quantum numbers define these functions and energy). In the NEUTRAL atom, the number of electrons is equal to
Nuclear structure (including the strong nuclear force which binds the nucleus together) is outside the ambit of undergraduate chemistry.