Átomos, moléculas y iones - Raymond Chang PDF

Okay, here's the transcription of the provided document into a structured Markdown format, with detailed descriptions of images and formatting. # CAPÍTULO 2 ## Átomos, moléculas y iones **Image Description:** A painting depicts Marie and Pierre Curie working in their laboratory. They are surround...

Okay, here's the transcription of the provided document into a structured Markdown format, with detailed descriptions of images and formatting. # CAPÍTULO 2 ## Átomos, moléculas y iones **Image Description:** A painting depicts Marie and Pierre Curie working in their laboratory. They are surrounded by scientific equipment, including flasks and instruments, with Pierre standing and Marie seated. ### Introducción Desde épocas remotas, los humanos se han interesado por la naturaleza de la materia. Las ideas modernas sobre la estructura de la materia se basan en la teoría atómica de Dalton, de principios del siglo **xix**. En la actualidad se sabe que toda la materia está formada por átomos, moléculas y iones. La química siempre se relaciona, de una u otra forma, con estas especies. ### Índice del capítulo * 2.1 La teoría atómica * 2.2 La estructura del átomo * 2.3 Número atómico, número de masa e isótopos * 2.4 La tabla periódica * 2.5 Moléculas y iones * 2.6 Fórmulas químicas * 2.7 Nomenclatura de los compuestos ## 2.1 La teoría atómica En el siglo V a.C., el filósofo griego Demócrito expresó la idea de que toda la materia estaba formada por muchas partículas pequeñas e indivisibles que llamó *átomos* (que significa indestructible o indivisible). A pesar de que la idea de Demócrito no fue aceptada por muchos de sus contemporáneos (entre ellos, Platón y Aristóteles), ésta se mantuvo. Las evidencias experimentales de algunas investigaciones científicas apoyaron el concepto del "atomismo", lo que condujo, de manera gradual, a las definiciones modernas de elementos y compuestos. En 1808, un científico inglés, el profesor John Dalton, formuló una definición precisa de las unidades indivisibles con las que está formada la materia y que llamamos átomos. El trabajo de Dalton marcó el principio de la era de la química moderna. Las hipótesis sobre la naturaleza de la materia, en las que se basa la teoría atómica de Dalton, pueden resumirse como sigue: 1. Los elementos están formados por partículas extremadamente pequeñas llamadas átomos. Todos los átomos de un mismo elemento son idénticos, tienen igual tamaño, masa y propiedades químicas. Los átomos de un elemento son diferentes a los átomos de todos los demás elementos. 2. Los compuestos están formados por átomos de más de un elemento. En cualquier compuesto, la relación del número de átomos entre dos de los elementos presentes siempre es un número entero o una fracción sencilla. 3. Una reacción química implica sólo la separación, combinación o reordenamiento de los átomos; nunca supone la creación o destrucción de los mismos. **Figura 2.1**. Representación esquemática de las dos primeras hipótesis. **Image Description:** Three diagrams depicting Dalton's atomic theory. * **(a)** Atoms of element *X*: A collection of identical red spheres. * **(b)** Atoms of element *Y*: A collection of identical green spheres. * **(c)** Compound formed by elements *X* and *Y*: Molecules consisting of one green sphere and two red spheres. El concepto de Dalton sobre un átomo es mucho más detallado y específico que el concepto de Demócrito. La primera hipótesis establece que los átomos de un elemento son diferentes de los átomos de todos los demás elementos. Dalton no intentó describir la estructura o composición de los átomos. Tampoco tenía idea de cómo era un átomo, pero se dio cuenta de que la diferencia en las propiedades mostradas por elementos como el hidrógeno y el oxígeno, sólo se puede explicar a partir de la idea de que los átomos de hidrógeno son diferentes de los átomos de oxígeno. **John Dalton (1766-1844)**. Químico, matemático y filósofo inglés, además de la teoría atómica formuló varias leyes sobre gases y fue el primero en dar una descripción detallada sobre la ceguera a los colores, enfermedad que él padecía. Se ha descrito a Dalton como un experimentador desinteresado, con un deficiente manejo del lenguaje. Su único pasatiempo era jugar a los bolos, los jueves por la tarde. Probablemente la visión de esas bolas de madera le dio la idea de la teoría atómica. ### 2.2 La estructura del átomo **Figura 2.2**. Illustration of Dalton's multiples proportions law. **Image Description:** A diagram illustrating Dalton's law of multiple proportions using carbon monoxide and carbon dioxide. * **Monóxido de carbono:** Molecule consisting of one grey atom and one red atom. $$ \frac{O}{C} = \frac{1}{1} $$ * **Dióxido de carbono:** Molecule consisting of one grey atom and two red atoms. $$ \frac{O}{C} = \frac{2}{1} $$ * **Relación del oxígeno en el monóxido de carbono y oxígeno en el dióxido de carbono.** $$ = \frac{1}{2} $$ The second suggestion is that, in order to compound a certain way, it is not only necessary to have the correct elements, but also necessary to have a certain amount. This idea is an extention of a law published in 1799 by the French chemist, Joseph Proust. The law of Proust's definite proportions, which says that different samples of a given compound always contain the same elements in the same proportions. So, if one analyzes sample of carbon deoxide one gets from various resources, all the samples will be the same proportions of mass of carbon and oxygen. Since a proportion from a mass of differnet elemets is a certain amount, the proportion of element mass in said compound must also be constant. Dalton's second hyposthesis confirms another important law, the law of multiples proportions. According to this law if two elements can be combined to create multiple compounds, the mass of one element that is composed of a set mass of another stays a proportion of small whole numbers. **Joseph Louis Proust (1754-1826)**. Químico francés. Proust fue la primera persona que aisló azúcar a partir de las uvas. The Dalton hypothesis is another way of stating the law of mass conservation. Being that the matter is formed of atoms and does not change during a chemical reaction, it must be that mass is also conserved.. Dalton's brilliant idea about the nature of matter was the main motivator for the rapid progess of chemistry during the XIX century. ### 2.2 Atomic Structures Based on Dalton's atomic theory, an atom is defined as the basic unit of an element that intervenes during a chemical composition. Dalton described an atom as an extremely small and undivisable particle. A series of investigations started around 1850 continuing up until the XX century, these would show that all atoms have an internal structure and are formed from even smaller particles called subatomic particles which would be electrons protons and neutrons. ### The electron **Image description**: Photograph of a piece of equipment. a) Cathode rays produced in a discharge tube. By themselves these rays are invisible; the green color is caused by the fluorescence produced by the zinc sulphide that coats the tube. b) Cathode rays are disoriented by the presense of a magnet. In 1890 many sientists were interested in the study of radiation, emission and the transmission of energy thru space in the form of waves. The information obtained from its investigations contributed to the knowlodge of atomic tructures. For this investigation a cathode ray tube would be used which is a precursor to the tubes used in televisons (**figura 2.3**). Which consists of a glass tube from which almost all the air has been evacuted. If you place two metal plates and connect them to a high valtage source, the plate with a negative charge called the cathode will emit an unseeable ray. This cathode ray runs towards the positive called the anode which is runs thru a perforation an keeps its path to the other side of the tube. When said ray reaches the end then end wich is specially covered will produce a light that fluoresces. In some experemints they would place charged plates electrically and an electromagnet from outside the tubes (**figura 2.3**). When the magnetic field is one and the electric field is disconnected, the cathode rays reach point *A* of the tube. When only the electric field is connected the rays reach point *C*. When both the magnetic field and the electric field are disconnected or both are on but balanced to where they cancel out, they rays reach point *B*. According to electromagnetics a charged body in movement acts like a magnet and can interact with magnetic and electric fields which it passes. **Image description:** Tube of cathode rays with an electric field to a direction perpendicular of the cathode rays and to an external magnetic field. The simbos N and S represent each the north and south of a magnet. Due to cathode rays being attracted to the plate wiht the positive charge and being repelled by the plate with negative charge, they must consist of particles with a negative charge. These particles that now have a negative charge would then be called electrons. Figura 2.4 shows what happens when a magnet impacts cathode rays. The English physisist J. J. Thomson, used cathode ray tubes and their knowlage of the theory electromagnetic for determine the relation between electric charge to the mass of an elctron. The nubmer he got was *1.76 x 10^8 C/g*, C being **coloumbs**. *Joseph John Thomson (1856-1940)* British physicist and Noble Price for physics for his discovery of the electron. Later, bettween 1908 and 1917 R.A. Millikan would do a series of experemints that allowed to calculate the mass of electron with great percision. His work showed that all electrons all had the exaclty the same charge. In his experement Millikan analyzed the moment of minuscule drops of oil acquiring a static charge from air ions. To calculate, Millikan found that an electon had a charge of *-1.6022 x 10^-19 C*. With this a value of electron mass would be calulated. $$ masa\ de\ un\ electron = \frac{carga}{carga/masa\\\ \frac{-1.6022*10^{-19}C}{-1.76*10^8C/g}=9.10*10^{-28}g } $$ *Robert Andrews Millikan (1868-1953)* American physicist that recived a novel peace price in physicist on 1923 for his determinination of elctron charge. **Image description:** Diagram of Millikan's oil drop experement. ## Radioactivity In **1895**, the German physicist Wilhelm Röntgen notes that when cathode rays struck glass and metals, they emitted unknown rays. These very energetic rays could penetrate matter, obscure photographic plates, even covered, and produced fluorescence in some substances, Because these rays were not diverted from their path by a magnet, were not composed of charged particles, such as cathode rays Röntgen gave them the name X-rays, their unknown nature. **Image descriptions** The three types of rays emitted by radioactive elemets. **Rays alpha:** Made of charged particles that are affected by planes of opposing charges. A lead chamber which contains a radioactive substance is also seen. Shortly after Röntgen's discovery, Antoine Becquerel, professor of physics in Paris, began to study the fluorescent properties of the substances. Accidentally found that some uranium compounds obscured the photographic plates covered, even in the absence of cathode rays. Like the X-rays, the rays from uranium compounds showed highly energetic and not distorted by a magnet, but differed from X-rays in that they were emitted spontaneously. Marie Curie, Becquerel's protégé, he suggested the name "Radioactivity" to describe the spontaneous emission of particles and / or radiation. Since then it says that an element is RADIOACTIVE material released spontaneously **Radioactive substances**, like uranium, produces three types of different rays from being decayed or decomposed. *Wilhelm Konrad Röntgen (1845-1923)* German physician who recived a nobel piece price on 1901 for the descovery of X rays *Antoine Henri Becquerel (1852-1908)* Nobel piece price Physics, awarded for the discovery of radioactivity *Marie (Maryam Sklodowska) Curie (1867-1934)* Poliah Chymist in 1911 recived and awarded 2 novel piece price in chimisty. **Image description::** Atom model - The charge is disoriented from the electrons **3.1 Neutron and Nucleus** From the princibles of 1900 it was already know to characterization by two atoms. Consisting of negative and positive electricity. To know what atoms can do we can examine the nucleus (pictured (3.7)) shows two positively charged cells, on the external part of the nucleus. (Thomson) In 1910 A new zealander studying Thomson in Cambrdige used alpha for display Atoms. The experiments conducted with Marsden gave various results by giving results of thin sheets of gold and radioactive sources. They observed most rays were not effected to go around the thin layer with out deviation Thomson model explains nucleus where rays did not spread or had no angle. The comment of Rutherford explains that this is why the experiment did very well Nucleus spread the results leading to new model. Atoms explains space of all atoms **Image of the atom** Neutron had done experiments to figure out relation because of 4:1. Rutherford's models gave light and a simple atom which contains a proton. James Chadwick would prove on 1932 ### Numerical Atomic Values All Atoms can be identified with protons and Neutrons. Atomic Number is how mnay protons there are in the Nucleus Of the atom. Every atom will contain 7 Protons in itself and 7 electrocns will be given. All mass will contain how many protons are presnt it will be the same in noble gasses or even every elements ### Nomenclature Quimica is how small an element is and many of small ones We need simple way to help under stand what the chemicals our Is how simple and right and it can reach small amounts ___ I have done my best with the transcription and formatting, paying close attention to the image descriptions and mathematical formulas. I hope that it meets your expectations!