It is in the d-block and it is a transition metal. Technetium is in the 7th group in the periodic table because it has 1 electron on its last shell. Also it is in the 5th period in the periodic table because it has 5 shells. Number of energy levels of Technetium is 5. Its electron shells are 2‚8‚18‚14‚1 as it is in the picture. Firstly‚ Russian chemist Dmitri Mendeleev‚ who is the creator of the periodic table‚ predicted Technetium’s existence. He called it eka-manganese because there was a missing
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The Development of the Periodic Table Although Dmitri Mendeleev is often considered the ‘father’ of the periodic table‚ the work of many scientists contributed to its present form. Between 1817-1829‚ Johann Dobereiner began to group elements with similar properties in to groups of three or triads. This began when he noticed that the atomic weights of strontium (Sr) were halfway between Calcium (Ca) and Barium (Ba). He stated that nature contained triads of elements in which the middle element
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Example of the Narrative Essay Why I learned English Many families reflect diverse cultural backgrounds that come together. My family’s roots are intertwined with several ethnic and cultural backgrounds. My mother’s parents are American‚ but her ancestors are originally from England and Germany. My father’s mother is Peruvian‚ but his father is Egyptian. I grew up in Peru with my parents in a quiet neighborhood of Lima. My paternal grandparents lived down the street from us‚ but my maternal grandparents
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Issue "It is possible to pass laws that control or place limits on people’s behaviour‚ but legislation cannot reform human nature. Laws cannot change what is in people’s hearts and minds." Essay “Man is born free but is in chains everywhere.”--- Jean-Jacques Rousseau‚ the Social Contract Nothing can be more apt than Rousseau’s quote in his book “The Social Contract”. It is more significant in today’s world because of the prevalent chaos and turmoil that surround us. Human nature‚ as such‚ is complex;
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The Periodic Properties of Atoms The Periodic Table: In the 1870’s‚ the Russian chemist Mendeleev developed the periodic table‚ based upon the relationship between the atomic weights of the elements and their chemical properties. As one ascends from lightest to heaviest elements‚ there is a periodic recurrence of chemical properties. For example‚ the elements with atomic numbers 2‚ 10‚ 18‚ 36‚ 54‚ and 86 all are chemically inert (the noble gases)‚ while those with atomic numbers one greater 3‚ 11
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Joy Jenkins Changing of the periodic table Today‚ the periodic table organizes the elements in horizontal rows‚ or periods‚ by order of increasing atomic number. The elements are also organized in vertical columns‚ or groups‚ based on similar physical characteristics and chemical behavior. I believe the periodic table will continue to evolve as new elements are discovered. One of the earliest attempts to organize the elements based on their chemical and physical properties was made by German
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1 18 IUPAC Periodic Table of the Elements 1 H 2 He helium hydrogen [1.007; 1.009] 2 3 4 Li beryllium 9.012 11 14 15 16 17 4.003 5 atomic number Be lithium [6.938; 6.997] 13 Key: 6 7 8 9 10 O F Ne boron carbon nitrogen oxygen fluorine neon [10.80; 10.83] B [12.00; 12.02] [14.00; 14.01] [15.99; 16.00] 19.00 20.18 12 13 14 15 16 17 18 Na
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The development of Periodic Table Elements such as gold and silver have been known since the earliest times. In 1649‚ a German alchemist‚ Hennig Brand made the first scientific discovery of an element‚ phosphorous. In the next 200 years‚ knowledge about the properties of elements and their compounds was gained. By 1869‚ 63 elements had been discovered in total. Scientists began to categorise those elements according to the similarities of their physical and chemical properties‚ which become the
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Lesson 3.01: History of the Periodic Table 1. Explain how scientific observations led to the development of‚ and changes to‚ the periodic table. Dmitri Mendeleev- first periodic table‚ organized 63 known elements according to properties‚ organized into rows and columns. He wrote names‚ mass and chemical properties on each. Julius lothar Meyer- independently worked in German ‚ similar to Mendeleev Henry Gwyn Jeffrey’s Moseley: worked with Ernest Rutherford experimented with 38 metals‚ he found that
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Promethium‚ Pm‚ is the 61st element on the Periodic Table. It was discovered in 1945 by Jacob A. Marinsky. It’s a metal‚ and named after the Greek God Prometheus. It is not naturally occurring‚ but can survive outside of a lab. Promethium has an atomic number of 61‚ which is the number of protons. Its atomic mass‚ protons+neutrons‚ is 145u. It is an isotope. This means that it has a different number of neutrons (84) than the number of electrons and protons (61). Every element changes states
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