...Atomic structure was originally devised by ancient Greek philosophers; However over recent years this theory has been modified and changed by many different scientists, such as Dalton, Thompson, Rutherford, Bohr and Chadwick. In 1808 John Dalton in his book “new systems of chemical philosophy.” Proposed that elements are composed of many discrete and invisible particles which are called atoms, atoms of the same element have identical properties and atoms of different elements have different properties. Compounds are composed of atoms of more than one element and also that a chemical reaction involves the separation, combining or rearranging of atoms. He was also responsible for part of the periodic table, as it was he who introduced the idea of chemical symbols, being the first to discover carbon dioxide. In the late 1800s and early 1900s J. J. Thomson conducted some experiments that did not agree with Dalton’s earlier atomic theory. He performed experiments using a Cathode ray tube. He conducted electricity through gases, causing a glow to be seen at the furthest end of the cathode tube. This proved that cathode rays must be made of something which has a negative charge. Thomson then concluded that atoms have tiny particles inside them called electrons which have a negative charge. He knew that on the whole atoms were neutral, so he came up with a theory that there must be a positive charge within the atom which would balance out the charge of the negative electrons. He suggested...
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... | | | | | | | | | | | |1.1 Atomic structure | |...
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...Natalia Blyznyuk Chemistry October 27, 2011 Essay Question:How is atomic structure related to the patters of the physical and chemical properties of an element illustrated on the periodic table? The periodic table consists of elements that are grouped together based on the knowledge that the elements have similar properties. The periodic table is arranged by periods and groups. The atomic number usually increases when moving across a row or period. The atomic structure of an atom consists of an electron, a proton, and a neutron. Electrons have light particles and a negative charge. Protons have heavier particles and have a positive charge. Neutrons also have heavier particles but do not a charge thus being neutral. Elements are commonly classified ad metals, nonmetals, or metalloids. The trend that elements contain are: Ionization energy, atomic radius, melting point/density, electronegativity, and reactivity. Atoms get bigger when one moves down the group and smaller when one moves to the right (moving across). The largest atomic radius is considered to be found in the bottom left corner of the periodic table. Along with high reactivity, the bottom left corner is also know to have low electronegativity and low ionization energy. The upper right corner on the other hand is the opposite. The upper right corner has high electronegativity, the smallest atomic radius, high ionization energy, and is very reactive. A broad amount of dense elements are found in the middle...
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...VASILEIOS-MARIOS GKORTSAS vasilisg@mit.edu 6.638 Term Paper Attosecond Pulse Generation Abstract: The word “attosecond” (1 as = 10-18 sec) entered the vocabulary of physics when sub-femtosecond pulses of UV/XUV light were established. High harmonic generation (HHG) is currently the only experimentally proven method for generating attosecond pulses. Attosecond science has opened the door to real-time observation and time-domain control of atomic-scale electron dynamics. In this work, we review the essentials of the generation of attosecond pulses and we mention the applications of attosecond science in the control of electronic motion. 1. Introduction The need for finer time resolution and the quest for higher peak power explain the continuous trend towards shorter laser pulses since the invention of the laser. The historical progress of ultra-short technology is summarized in Figure 1. The first pulse lasers had duration of several hundreds of microseconds. The invention of Q-switching (Hellwarth, 1961) reduced the pulse length to 10 ns (four orders of magnitude decrease). The invention of laser mode locking (DiDomenico, 1964; Hargrove et al., 1964; Siegman, 1970) accompanied by broad gain laser media (Shank and Ippen 1974) further reduced the duration to less than 1 ps (another four orders of magnitude decrease). The ring cavity with intra-cavity prism compensation of the group velocity dispersion produced pulses of 6 fs (Fork et al, 1987)...
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...Name Lab Section Date The Mole Concept and Atomic Weights Text Reference: Tro, Chemistry: Structure and Properties Section 2.8 - Atoms and the Mole: How Many Particles? Section 1.9 – Atomic Mass: The Average of an Element’s Atoms The purpose of this activity is to better understand the concepts of relative atomic mass, counting by weighing and the mole. Per cent composition and average atomic mass are included. Part I. Relative Atomic Masses and the Mole – Early Method When John Dalton proposed his atomic theory, he stated that the atoms of each element had a characteristic mass. He carried out experiments to determine the relative atomic mass of each element. To do this, he had to establish a standard because a single atom was too small to weigh. The standard he chose was that the mass of hydrogen would be set equal to 1.000. In a simple experiment, Dalton would measure the grams of an element such as sulfur that reacted with 1.00 gram of hydrogen. For sulfur, the reacting mass was found to be 32.0 grams, and so 32.0 was the relative mass of sulfur with respect to the standard hydrogen. (Note: The current standard for atomic mass is the most abundant isotope of carbon, C-12, with an assigned mass of exactly 12.000 amu.) The following activity will demonstrate how the relative mass method works. 1. Weigh five of the red color balls to three decimal places. Be sure to tare out the mass of the plastic cup. Record the mass in the table below. 2. Weigh five...
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...Sherrilyn Ling History of the Universe Lenny Tevlin October 5, 2015 6. Briefly describe the structure and size of an atom. How big is the nucleus in comparison to the entire atom? Atoms are extremely small; millions of atoms could fit end to end across a period at the end of a sentence. Protons and neutrons are found in the tiny nucleus at the center of the atom. The rest of the atom’s volume is made up of electrons, which surround the nucleus. The nucleus is very small compared to the atom as a whole, but it contains a majority of the atom’s mass. 7. What determines an atom’s atomic number? What determines its atomic mass number? Under what conditions are two atoms different isotopes of the same element? What is a molecule? The atomic number is the number of protons in a chemical element’s nucleus. The atomic mass number is the combined number of protons and neutrons in an atom. Isotopes occur when versions of an element have the same number of protons but a different number of neutrons. A molecule is formed when atoms of the same element combine. 8. What is electrical charge? Will an electron and a proton attract or repel each other? Will two elections attract or repel each other? Explain. Electrical charge is a fundamental property that describes how strongly an object will interact in electromagnetic fields. Protons and electrons attract each other, but two electrons repel. Protons have a positive charge and electrons have a negative charge; like charges repel...
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...symbol at least 4 trace elements. An element is the simplest form of matter and cannot be broken down into simpler substances in a chemical reaction. Elements have unique properties. There are 91 natural occurring elements, 24 of these elements play a normal physiological role in humans. The 4 most abundant elements found in the body are oxygen (O), carbon(C), Hydrogen (H) and Nitrogen (N). there are 8 major or less elements in the body include calcium(Ca), phosphorus(P), sulfur(S), potassium(K), sodium(Na), chlorine(Cl), Magnesium(Mg) and iron(Fe). Trace elements account 0.7% of body weight and play a vital roles in physiology, they include, cobalt (Co), copper (Cu), fluorine (F), and iodine (I) Define the term ‘atom’. Discuss the structure of an atom including A) the name of the 3 major types of subatomic particles, B) the electrical properties of each of these subatomic properties, and C) the arrangement of these subatomic particles in the atom including a brief description of electron shells or energy levels. An atom is the smallest unit of an element which consists of a proton (P), neutron (n) and an electron (e). Protons are positively charges, electrons are negatively charged and neutrons have no charges i.e. are neutral. Both the proton and neutron are located inside the nucleus while the electron is located outside the nucleus. Electrons have low mass compared to the weight of the protons and neutrons inside the nucleus. Electrons determine the chemical properties...
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...notes will be permitted; calculators are permitted but must not connect to the internet or to outside sources of information. A periodic table with atomic numbers and atomic masses will be provided. There will be 26 questions: most multiple choice but some short answer and some calculations. You will be required to know the material and how to apply that knowledge. You will be expected to know basic conversion factors (grams –pounds, cm – in., ft – in., temp conversion equations, meanings of prefixes: milli-, centi-, kilo-, mega-, etc, but not the rarer ones). Other required conversion info will be provided (specific heats, etc.). No nomenclature on this exam. Topics and concepts to be covered: (Textbook: Chapt 1, 2, 3, 4, 10(pp288-302), 11.) Scientific method Significant figures, calculations, and scientific notation Unit conversions – temp., mass, length, volume, area, time Density; calculation of and uses of Physical and Chemical properties Physical and Chemical changes Qualitative vs quantitative observations and measurements Conservation of mass and energy Heat/temperature relationships and conversions including temp increases/decreases; heat absorbed/ released; specific heat computations; phase changes Atomic theory/atomic and electronic structures of atoms and elements; ions and ionic charges Sub-atomic particles Periodic table: what it is, uses, information contained in it Names of certain groups (columns) in the periodic table (covered in class) ...
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...Postulates of Dalton’s Atomic Theory The main points of Dalton’s atomic theory, an explanation of the structure of matter in terms of different combinations of very small particles, are given by the following postulates: 1. All matter is composed of indivisible atoms. An atom is an extremely small particle of matter that retains its identity during chemical reactions. 2. An element is a type of matter composed of only one kind of atom, each atom of a given kind having the same properties. Mass is one such property. Thus, the atoms of a given element have a characteristic mass. 3. A compound is a type of matter composed of atoms of two or more elements chemically combined in fixed proportions. The relative numbers of any two kinds of atoms in a compound occur in simple ratios. Water, for example, a compound of the elements hydrogen and oxygen, consists of hydrogen and oxygen atoms in the ratio of 2 to 1. 4. A chemical reaction consists of the rearrangement of the atoms present in the reacting substances to give new chemical combinations present in the substances formed by the reaction. Atoms are not created, destroyed, or broken into smaller particles by any chemical reaction. Main Points of the Bohr Model Postulate 1: An electron in an atom moves in a circular orbit under the influence of coulomb attraction between the electron and the nucleus obeying the rules of classical mechanics. Postulate 2: An atom can exist in certain allowed or stationary states, with each...
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...AS/A Level GCE GCE Chemistry A OCR Advanced Subsidiary GCE in Chemistry A H034 OCR Advanced GCE in Chemistry A H434 Vertical black lines indicate a significant change to the previous printed version. © OCR 2008 version 2 – February 2008 QAN 500/2425/5 QAN 500/2347/0 Contents 1 About these Qualifications 1.1 1.2 1.3 1.4 1.5 The Three-Unit AS The Six-Unit Advanced GCE Qualification Titles and Levels Aims Prior Learning/Attainment 4 4 4 5 5 5 2 Summary of Content 2.1 2.2 AS Units A2 Units 6 6 7 3 Unit Content 3.1 3.2 3.3 3.4 3.5 3.6 AS Unit F321: Atoms, Bonds and Groups AS Unit F322: Chains, Energy and Resources AS Unit F323: Practical Skills in Chemistry 1 A2 Unit F324: Rings, Polymers and Analysis A2 Unit F325: Equilibria, Energetics and Elements A2 Unit F326: Practical Skills in Chemistry 2 8 8 20 38 40 51 62 4 Schemes of Assessment 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 AS GCE Scheme of Assessment Advanced GCE Scheme of Assessment Unit Order Unit Options (at AS/A2) Synoptic Assessment (A Level GCE) Assessment Availability Assessment Objectives Quality of Written Communication 64 64 65 66 66 66 67 67 68 5 Technical Information 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 Making Unit Entries Making Qualification Entries Grading Result Enquiries and Appeals Shelf-life of Units Unit and Qualification Re-sits Guided Learning Hours Code of Practice/Subject Criteria/Common Criteria Requirements Arrangements for Candidates with Particular...
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...such as cosmic ray spallation. New atoms are also naturally produced on Earth as radiogenic daughter isotopes of ongoing radioactive decay processes such as alpha decay, beta decay, spontaneous fission, cluster decay, and other rarer modes of decay. Of the 98 naturally occurring elements, those with atomic numbers 1 through 40 are all considered stable. At least one isotope of each element with atomic numbers 41 through 82 is apparently stable (except technetium, element 43 and promethium, element 61, which have no stable isotopes) but theoretically unstable (in that their fission would release energy) and thus possibly mildly radioactive.[10][11][not in citation given] The half-lives of elements 41 through 82 are so long, however, that their radioactive decay remains undetected by experiment. These "theoretical radionuclides" have half-lives at least 100 million times longer than the estimated age of the universe.[citation needed] Elements with atomic numbers 83 through 98 are unstable to the point that their radioactive decay can be detected. Some of these elements, notably bismuth (atomic number 83), thorium (atomic number 90), uranium (atomic number 92) and plutonium (atomic number 94), have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced the heavy elements before the formation of our solar system. For example, at over 1.9×1019 years,...
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...Attendance for lectures, tutorials and experiments are compulsory for every student. Main Text: Kotz, J. C., Treichel, P. M., & Townsend, J. R. (2012). Chemistry & chemical reactivity (8th ed.). Belmont, CA: Thomson Brooks/Cole. Total 1. Coursework 50% a) Test 1 & 2 (15% each) b) Experiment (20%) 2. Final Examination 50% Grand total 100% Chapter Scopes FHSC1114 PHYSICAL CHEMISTRY CHAPTER 1 Principle of Chemistry Relative Atomic Masses of atoms & molecules Mass number & atomic number Atomic structure (neutrons, protons & electrons) Mole concept & conversion Avogadro’s concept Empirical & molecular formulae Isotopes FHSC1114 Physical Chemistry 1 Centre for Foundation Studies, UTAR Objectives To define relative atomic masses of atoms & molecules To define & determine mass no. & atomic no. To determine no. of neutrons, protons & electrons To understand mole concept & Avogadro’s concept To determine the empirical & molecular formulae Structure of An Atom Atomic Composition 3 subatomic particles made up all atoms: Electrically positive protons Electrically neutral neutrons Electrically negative electrons Table: Properties & Location of Protons, Neutrons & Electrons In Atom Subatomic Symbol Relative Mass Mass Location Particle electrical (g) (amu) charge Proton p+ +1 1.6726 1 In the x 10-24 nucleus...
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...|Democritus |"by convention bitter, by convention sweet, but in reality atoms and void" | | |1704 |Isaac Newton |Proposed a mechanical universe with small solid masses in motion. | |1803 |John Dalton |Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass. | |1832 |Michael Faraday |Studied the effect of electricity on solutions, coined term "electrolysis" as a splitting of molecules with electricity, | | | |developed laws of electrolysis. Faraday himself was not a proponent of atomism. | |1859 |J. Plucker |Built one of the first gas discharge tubes ("cathode ray tube"). | |1869 |Dmitri Mendeleev |Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic | | | |functions of the their atomic weights". This became known as the Periodic Law. | |1873 |James Clerk Maxwell |Proposed electric and magnetic fields filled the void. | |1879 |Sir William Crookes |Discovered...
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...brilliantly developed the application of X-ray spectra to study atomic structure; Moseley's discoveries resulted in a more accurate positioning of elements in the Periodic Table by closer determination of atomic numbers. In 1913, while working at the University of Manchester, Moseley observed and measured the X-ray spectra of various chemical elements obtained by diffraction in crystals. Through this he discovered a systematic relation between wavelength and atomic number. This discovery is now known as the Moseley’s law Both the apparent irregularities in the location of elements such as argon and potassium and the positioning of the rare earth (inner transition) elements in the periodic table could now be elucidated on the basis of atomic number. In addition, Moseley showed that there were gaps in the atomic number sequence at numbers 43, 61, 72, and 75. These spaces are now known, respectively, to be the places of the radioactive synthetic elements technetium and promethium. Moseley predicted the two more undiscovered elements, those with the atomic numbers 72 and 75, and gave very strong evidence that there were no other gaps in the Periodic Table between the elements aliminium (atomic number 13) and gold (atomic number 79). Moseley's law provided a reasonably complete experimental set of data supporting the (at that time new from 1911) Ernest Rutherford/Antonius Van den Broek concept of the atom, in which atomic number is understood as representing physically exactly the...
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...The Element Neon Discovery of Neon The periodic table is prearranged like a large grid. Each element is placed in a specific location because of its atomic structure. The periodic table consists of one hundred eighteen elements in total. Neon is one of those elements within the Periodic table and NE symbolizes this element. Neon has an atomic number of 10 which is the number of protons in the nucleus and an atomic weight of approximately 20 which is the average mass of the atom. The interesting fact is that Neon gets its name from the Greek word “Neos” which means new. The element Neon was discovered by a Scottish chemist named Sir William Ramsay and an English chemist named Morris M. Travers at University College London. These two had also...
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