Nursing Entrance Exam

a wave simultaneously. Heisenberg’s uncertainty principle looks at this odd truth about reality and says you cannot watch an electron orbit the nucleus as you would watch the Earth orbit the sun. Rather, you should observe only one of the electron’s physical characteristics at a time, either viewing it as a particle in a fixed position outside the nucleus or as a wave encircling the nucleus like ahalo. Additionally, planets orbiting their stars can orbit at any distance they want. In fact, every object in our solar system has an elliptical orbit, meaning that they all move in an oval shape, getting closer and farther from the sun at various points. Electrons cannot do this under any circumstances. Atoms have what are known as electron shells, which are the levels that an electron is able to inhabit. Between these shells, electrons cannot exist; instead, they jump from one to the next instantaneously. Each electron shell can hold a different number of atoms. When a shell fills up, additional electrons fill the outer shells. The outermost shell of any atom is called the valence shell, and it is the electrons in this shell that interact with the electrons of other atoms. The important thing about the valence shell is that each electron shell has a specific number of electrons that it can hold, and it wants to hold that many. When atoms join, their connecting valence electrons take up two valence shell spots, one on each atom. This means that the fewer electrons an atom has in its valence shell, the more likely it is to interact with other atoms. On the other hand, the more electrons it has, the less likely it is to interact. Additionally, electrons are able to momentarily jump from one electron shell to the next if they are hit with a burst of energy from a photon. When photons hit atoms, the energy is briefly absorbed by the electrons, and this momentarily knocks them into higher “orbits”. The particular “orbit” the electron is knocked into depends on the type of atom, and when the electron gives up its higher energy level, it reemits a photon at a slightly different wavelength than the one it absorbed, providing a characteristic signal of that atom and showing into exactly which “orbit” the electron was knocked. This is the phenomenon responsible for spectral lines in light and is the reason we can tell what elements make up stars and planets simply by looking at them. Unlike protons and neutrons, electrons are a fundamental particle on their own; they are also called leptons. Electrons have a negative charge that is generally balanced out by the positive charge of their atom’s protons. Charged atoms, which have either gained or lost an electron for various reasons, are called ions. Ions, like isotopes, have the same properties that the regular element does; they simply have different tendencies towards reacting with other atoms. Electrons have a mass of 9.1094 × 10- 31 kg and a -½ spin. Eleme t The concept of a chemical element is related to that of a chemical substance. A chemical element is a substance that is made up of a single type of atom. A chemical element is characterized by a particular number of protons in the nuclei of its atoms; this number is known as the element’s atomic number. For example, all atoms containing six protons in their nuclei are atoms of the element carbon, and all atoms with 92 protons in their nuclei are atoms of the element uranium.

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