Protons are held together by a strong nuclear force, stronger than electrostatic. Therefore it overcomes the repulsion between protons, but only acts over very short distances (i.e. within the nucleus)
Chemical properties remain the same as there is still the same electron configuration, however isotopes have different physical properties as they have a different number of neutrons, therefore affecting the mass.
An instrumental method of analysis that can be used to find: 1) the abundance and mass of each isotope of an element, 2) the Mr of particular compounds, 3) determination of Ar.
The idea of an electron moving as a charged particle at a fixed energy level cannot be explained mathematically. The solution was to consider electrons having wave or particle duality, described by quantum mechanics.
Successive IEs are always more different and greater than the previous one (more energy required) because electrons are being removed from a more species