The atomic number of the element is 74

Physics compact, basic knowledge 5, textbook

Heat and Energy 5 74 Thermodynamics RG 5 and G 6.1 The electron shell The number of electrons in a neutral atom is called atomic number (symbol Z). All atoms of a chemical element have the same atomic number, eg: hydrogen 1, carbon 6, oxygen 8, ... Based on their atomic number, all elements can be classified in the periodic table of chemical elements. Elements with similar chemical properties are grouped in columns. These elements have the same number of external electrons. In the compilation of the periodic table, which D. I. Mendeleev and J. L. Meyer succeeded in doing independently of one another in 1869, a few places remained vacant. Due to the position of the free spaces in the periodic table, some chemical properties of the then unknown chemical elements could be inferred. This made a targeted search for these new elements possible (eg germanium). Today more than 100 elements are known. Under everyday conditions, 11 elements are gaseous (hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon, radon), only two elements are liquid (bromine and mercury), all of them widely. Ren elements are fixed. The elements TechnetiumTc (Z = 43), Promethium Pm (Z = 61) and all elements with Z> 83 have unstable nuclei. They disintegrate through radioactive processes and are converted into other elements in the process. The heaviest element found in nature is Plutonium Pu (Z = 94). All heavier elements can only be produced artificially through nuclear reactions (super-heavy elements). Note: The manufacture of super-heavy elements is a current research area in nuclear physics. Accelerators are used to bring the ions of heavy elements (eg lead) to high speeds and then shoot them together. Sometimes this creates the nuclei of super-heavy atoms, which are usually extremely short-lived. However, one assumes at Z ≈ 126 elements that are more durable than the previously known super-heavy elements. A1 Try to find out something about the origin of the elements! 5.1.2 W1 A2 Find the gaseous and liquid elements in a periodic table and name them! A3 Get information about D. I. Mendeleev and J. L. Meyer from an encyclopedia or the Internet! A4 Estimate the fraction of the mass of an atom that comes from the electrons! A5 In which parts of the periodic table are metals found, and where are non-metals? A6 The sun consists mainly of hydrogen. A hydrogen atom has a mass of around 1.7 ∙ 10 −27 kg. Calculate the mass of the sun! A7 Look for the heaviest element with stable atomic nuclei in the periodic table! A8 Enter the ordinal number of the heaviest currently known element! Electric forces prevail between the electrically charged atomic nuclei and the electron shells. Depending on how strongly atomic nuclei influence the electron shells of neighboring atoms, a distinction is made between the following cases: 1) Atomic form: We speak of atomic form when an element is present in individual atoms (e.g. noble gases). The electron shells around each nucleus contain exactly as many electrons as the atomic number of the element indicates. The forces between the atomic nuclei and the foreign electron shells are too small to enable a stable bond between the atoms that can withstand the movement of heat. 2) Chemical compound: The electrical forces between neighboring atomic particles are sufficient to enable a stable structure to counteract the movement of heat. Chemical processes are based on the electrical properties of the electron shells. The atomic nuclei remain separated during chemical transformations and their properties remain unchanged. W1 W1 E1 E1 W1 E1 E1 Every chemical bond is based on electrical forces. Chemical bond For testing purposes only - property of the publisher öbv

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