1Physical properties can change states without changing the molecular structure, but this is not the case for chemical properties.With chemical properties the chemical identity of the substance is changed, this is not the case with physical properties.With chemical properties the structure of the material changes, while the structure does not change in the case of physical properties.A chemical reaction occurs before a chemical property becomes evident, while no chemical reaction is needed for a physical property to become visible.Chemical properties, unlike physical properties, can be used to predict how substances will react.
5Well, 14N and 15N are two isotopes of nitrogen, meaning that they have the same amount of protons but different amount of neutrons.
So, the first thing we will notice is that they have the same atomic number.
We know that the mass number of an atom is the sum of its proton number and neutron number. Since the two isotopes have different amount of neutrons, they will have different masses, and we conclude that their mass numbers are different from each other.
Nothing really changes in their atomic structure. They will have different amount of neutrons, there are 7 neutrons in 14N and 8 neutrons in 15N. Aside from that, they will have the same amount of electrons.
6.Radioactive isotope, also called radioisotope, radionuclide, or radioactive nuclide, any of several species of the same chemical element with different masses whose nuclei are unstable and dissipate excess energy by spontaneously emitting radiation in the form of alpha, beta, and gamma rays.
uses
Radioactive isotopes have many useful applications. In medicine, for example, cobalt-60 is extensively employed as a radiation source to arrest the development of cancer. Other radioactive isotopes are used as tracers for diagnostic purposes as well as in research on metabolic processes. When a radioactive isotope is added in small amounts to comparatively large quantities of the stable element, it behaves exactly the same as the ordinary isotope chemically; it can, however, be traced with a Geiger counter or other detection device. Iodine-131 has proved effective in treating hyperthyroidism. Another medically important radioactive isotope is carbon-14, which is used in a breath test to detect the ulcer-causing bacteria Heliobacter pylori.
4.There are many different levels of explanation for this question. Strangely enough most of them will dive into quantum electrodynamics, Feynman diagrams and exchange of virtual photons...
I will try a simpler path that still carries some explanation.
When you put two charges at a distance, they deform the -- otherwise flat -- electromagnetic (EM) potential field. Depending on whether the two charges have the same sign or not, the EM field will be deformed differently.
check the attachment
deformation energy created by the single charge q1,2 had it been alone in the universe.
The total energy is thus expressed as the sum of the individual contributions coming from each particles plus a correction due to the fact that, when the charges are close enough, the EM field deformations generated by one charge will be affected by the deformations created by the other.
The interpretation that comes out of it is that when the charges have opposite sign, each charge acts as a deformation "sink" for the other charge deformations of opposite sign; that is the deformations generated by one particle are weakened by the deformations generated by the other. This deformation weakening effect is all the more important as the charges get closer and closer until they eventually overlap and yield (in principle) a zero deformation field. Since the universe seems to prefer low energy states, charges with opposite signs attract one another as a consequence.
The opposite is true of charges with the same sign whereby the deformations generated by one charge is simply enhanced by the presence of the other charge. Thus the EM field has more "curvature" energy to store than what it would have had if the charges had been accounted separately (or if they were infinitely far from one another). Since Nature again prefers low energy states, this implies that charges with the same sign will repel each other.
