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Kentucky Core Content SC-08-1.1.1 Students will: interpret models/representations of elements; classify elements based upon patterns in their physical (e.g., density, boiling point, solubility) and chemical (e.g., flammability, reactivity) properties. Core Content Cont. SC-08-1.1.2 Students will understand that matter is made of minute particles called atoms, and atoms are composed of even smaller components. The components of an atom have measurable properties such as mass and electrical charge. Each atom has a positively charged nucleus surrounded by negatively charged electrons. The electric force between the nucleus and the electrons holds the atom together. Core Content Cont. SC-08-1.1.3 Students will understand that the atom’s nucleus is composed of protons and neutrons that are much more massive than electrons. Investigating Atoms and Atomic Theory Students should be able to: Describe the particle theory of matter. Use the Bohr model to differentiate among the three basic particles in the atom (proton, neutron, and electron) and their charges, relative masses, and locations. Compare the Bohr atomic model to the electron cloud model with respect to their ability to represent accurately the structure of the atom. Journal 3-16-2010 Why do physicists study particles? Physicists study particles because everything is made of them, including us! People have been trying to understand what the Universe is made of forever. One of the earliest theories said that everything could be built from just four elements, Earth, Air, Fire and Water. This was a great scientific theory because it was simple. But it had one big drawback: it was wrong. WHY? Atomos: Not to Be Cut The History of Atomic Theory Atomic Models This model of the atom may look familiar to you. This is the Bohr model. In this model, the nucleus is orbited by electrons, which are in different energy levels. A model uses familiar ideas to explain unfamiliar facts observed in nature. A model can be changed as new information is collected. The atomic model has changed throughout the centuries, starting in 400 BC, when it looked like a billiard ball → Who are these men? In this lesson, we’ll learn about the men whose quests for knowledge about the fundamental nature of the universe helped define our views. Democritus 400 BC This is the Greek philosopher Democritus who began the search for a description of matter more than 2400 years ago. He asked: Could matter be divided into smaller and smaller pieces forever, or was there a limit to the number of times a piece of matter could be divided? Atomos His theory: Matter could not be divided into smaller and smaller pieces forever, eventually the smallest possible piece would be obtained. This piece would be indivisible. He named the smallest piece of matter “atomos,” meaning “not to be cut.” Atomos To Democritus, atoms were small, hard particles that were all made of the same material but were different shapes and sizes. Atoms were infinite in number, always moving and capable of joining together. This theory was ignored and forgotten for more than 2000 years! The eminent philosophers of the time, Aristotle and Plato, had a more respected, Aristotle and Plato favored the earth, fire, air and water approach to the nature of matter. (and Their ideas held sway because of their eminence as philosophers. The atomos idea ultimately was buried for approximately 2000 years. wrong) theory. Dalton’s Model In the early 1800s, the English Chemist John Dalton performed a number of experiments that eventually led to the acceptance of the idea of atoms. Dalton’s Theory He deduced that all elements are composed of atoms. Atoms are indivisible and indestructible particles. Atoms of the same element are exactly alike. Atoms of different elements are different. Compounds are formed by the joining of atoms of two or more elements. . Thistheory became one of the foundations of modern chemistry. Thomson’s Plum Pudding Model In1897, the English scientist J.J. Thomson provided the first hint that an atom is made of even smaller particles. Thomson Model He proposed a model of the atom that is sometimes called the “Plum Pudding” model. Atoms were made from a positively charged substance with negatively charged electrons scattered about, like raisins in a pudding. Thomson Model Thomson studied the passage of an electric current through a gas. As the current passed through the gas, it gave off rays of negatively charged particles. Thomson Model Where did they come surprised This from? Thomson, because the atoms of the gas were uncharged. Where had the negative charges come from? Thomson concluded that the negative charges came from within the atom. A particle smaller than an atom had to exist. The atom was divisible! Thomson called the negatively charged “corpuscles,” today known as electrons. Since the gas was known to be neutral, having no charge, he reasoned that there must be positively charged particles in the atom. But he could never find them. Rutherford’s Gold Foil Experiment In 1908, the English physicist Ernest Rutherford was hard at work on an experiment that seemed to have little to do with unraveling the mysteries of the atomic structure. Rutherford’s experiment Involved firing a stream of tiny positively charged particles at a thin sheet of gold foil (2000 atoms thick) Most of the positively charged “bullets” passed right through the gold atoms in the sheet of gold foil without changing course at all. Some of the positively charged “bullets,” however, did bounce away from the gold sheet as if they had hit something solid. He knew that positive charges repel positive charges. http://chemmovies.unl.edu/ChemAnime/R UTHERFD/RUTHERFD.html This could only mean that the gold atoms in the sheet were mostly open space. Atoms were not a pudding filled with a positively charged material. Rutherford concluded that an atom had a small, dense, positively charged center that repelled his positively charged “bullets.” He called the center of the atom the “nucleus” The nucleus is tiny compared to the atom as a whole. Rutherford Rutherford reasoned that all of an atom’s positively charged particles were contained in the nucleus. The negatively charged particles were scattered outside the nucleus around the atom’s edge. Bohr Model In1913, the Danish scientist Niels Bohr proposed an improvement. In his model, he placed each electron in a specific energy level. Bohr Model According to Bohr’s atomic model, electrons move in definite orbits around the nucleus, much like planets circle the sun. These orbits, or energy levels, are located at certain distances from the nucleus. Wave Model The Wave Model Today’s atomic model is based on the principles of wave mechanics. According to the theory of wave mechanics, electrons do not move about an atom in a definite path, like the planets around the sun. The Wave Model In fact, it is impossible to determine the exact location of an electron. The probable location of an electron is based on how much energy the electron has. According to the modern atomic model, an atom has a small positively charged nucleus surrounded by a large region in which there are enough electrons to make an atom neutral. Electron Cloud: A space in which electrons are likely to be found. Electrons whirl about the nucleus billions of times in one second They are not moving around in random patterns. Location of electrons depends upon how much energy the electron has. Electron Cloud: Depending on their energy they are locked into a certain area in the cloud. Electrons with the lowest energy are found in the energy level closest to the nucleus Electrons with the highest energy are found in the outermost energy levels, farther from the nucleus. Indivisible Electron Nucleus Orbit Electron Cloud Greek X Dalton X Thomson X Rutherford X X Bohr X X X Wave X X X List 3 key points from today’s lesson on atomic theory history. Journal 3-17-10 Compare and contrast physical and chemical changes in matter. You may use any graphic organizer you wish to complete this journal. Atomic Structure Core Content for Assessment SC-08-1.1.3 Students will understand that the atom’s nucleus is composed of protons and neutrons that are much more massive than electrons. SC-08-1.1.2 Students will understand that matter is made of minute particles called atoms, and atoms are composed of even smaller components. The components of an atom have measurable properties such as mass and electrical charge. Each atom has a positively charged nucleus surrounded by negatively charged electrons. The electric force between the nucleus and the electrons holds the atom together. Structure of an atom (page 256 in Sciencesaurus) Nucleus – The core of an atom. Contains protons and neutrons. Protons – Positively (+) charged particles found in the nucleus of an atom. Neutrons – Neutrally charged particles found in the nucleus of an atom. Electrons – Negatively (-) charged particles found outside the nucleus of an atom. Structure of an atom Valence electron – the fartheset away or most loosely held electrons which help determine how elements bond. Electron Dot Diagram – A diagram in which each dot represents one electron in the outer valence “shell”. (pg 268 in Sciencesaurus) Isotopes – Atoms of the same element that have different number of neutrons (eg. Carbon) 3rd Verse: 1st Verse: They’re tiny and they’re Neutrons can be found, Where protons hang teeny, around; Much smaller than a beany, Electrons they surround They never can be seeny, The Atoms Family. The Atoms Family. Chorus Chorus Chorus: 2nd Verse: Together they make gases, They are so small. (Snap, snap) And liquids like molasses, They’re round like a ball. And all the solid masses, (Snap, snap) The Atoms Family They make up the air. Chorus They’re everywhere. Can’t see them at all. (Snap, snap) They’re tiny and they’re teeny, Much smaller than a beany, They never can be seeny, The Atoms Family. They are so small. (Snap, snap) They’re round like a ball. (Snap, snap) They make up the air. They’re everywhere. Can’t see them at all. (Snap, snap) Together they make gases, And liquids like molasses, And all the solid masses, The Atoms Family They are so small. (Snap, snap) They’re round like a ball. (Snap, snap) They make up the air. They’re everywhere. Can’t see them at all. (Snap, snap) Neutrons can be found, Where protons hang around; Electrons they surround The Atoms Family. Journal March 17, 2010 What is the name of this atom model and who was the scientist that created it? Reviewing Matter Three principal states of matter Solid Liquid Gas States of matter Solid: molecules are tightly packed together; definite shape and volume Liquid: molecules are able to move around, but are still bonded; no definite shape, but definite volume Viscosity: the resistance of a liquid to flowing. Highviscosity flows slowly Low viscosity flows quickly Gas: molecules are spread apart, filling the space available; no definite shape or volume Characteristics of matter Boiling point (vaporization): the temperature at which a liquid changes to a gas Melting point: the temperature at which a solid changes to a liquid Condensation point: the temperature at which a gas turns to a liquid (the same temperature as the boiling point) Freezing point: the temperature at which a liquid changes to a solid (the same temperature as the melting point) Changes in Matter Physicalchange: alters the form of a substance, but not its identity Examples: mixing salt and water, freezing water Chemical change: substances combine or break apart to form new substances burning wood, heating sugar to Examples: make caramel Types of Matter Mixtures: two or more substances that are in the same place but are not chemically combined Examples: Kool-aid, sea water Puresubstances: made of only one kind of matter and has definite properties. Pure Substances Elements: a substance that cannot be broken down into other substances by chemical or physical means Examples: iron, copper, aluminum Compounds: a substance made of two or more elements that are chemically combined Examples: sugar, salt Clean sheet of paper Put your name on the paper Number your page 1-22 On the next slide, you will see a list of items, place a “P” next to the number if the change is physical Place a “C” next to the number if the change is chemical 1. Glass breaking 2. Hammering wood together to build a playhouse 3. A rusting bicycle 4. Melting butter for popcorn 5. Glassblower creating sculptures out of glass 6. Freezing chocolate-covered bananas 7. Separating sand from gravel 8. Spoiling food 9. Burning toast 10. Making salt water to gargle for a sore throat 11. Mixing lemonade powder into water 12.Cream being whipped 13.Water evaporating from a pond 14.Cutting grass 15.Burning leaves 16.Humidifier putting moisture into the air 17.Corroding metal 18.Bleaching your hair 19.Fireworks exploding 20.Squeezing oranges to get orange juice 21.Frying an egg 22.Pouring milk on your oatmeal Journal 3-18-10 Hint: Look at Section L page 169 1. Describe the arrangement of the periodic table. 2. Explain what kind of information can be found on the periodic table? Elements and the Periodic Table (page 265 in Sciencesaurus) Core Content for SC-08-1.1.1 Assessment Students will: interpret models/representations of elements; classify elements based upon patterns in their physical (e.g., density, boiling point, solubility) and chemical (e.g., flammability, reactivity) properties. Models enhance understanding that an element is composed of a single type of atom. Organization/interpretation of data illustrates that when elements are listed according to the number of protons, repeating patterns of physical (e.g., density, boiling point, solubility) and chemical properties (e.g., flammability, reactivity), can be used to identify families of elements with similar properties. DOK 2 Why is the Periodic Table important to me? The periodic table is the most useful tool to a chemist. You get to use it on every test. It organizes lots of information about all the known elements. Pre-Periodic Table Chemistry … …was a mess!!! No organization of elements. Imagine going to a grocery store with no organization!! Difficult to find information. Chemistry didn’t make sense. Dmitri Mendeleev: Father of the Table HOW HIS SOME WORKED… PROBLEMS… Put elements in rows He left blank spaces by increasing atomic for what he said were undiscovered weight. elements. (Turned Put elements in out he was right!) columns by the way He broke the pattern they reacted. of increasing atomic weight to keep similar reacting elements together. The Current Periodic Table Mendeleev wasn’t too far off. Now the elements are put in rows by ATOMIC increasing NUMBER!! The horizontal rows are called periods and are labeled from 1 to 7. The vertical columns are called groups are labeled from 1 to 18. Groups Vertical columns of elements in the periodic table. Also known as Families. Families may be one column, or several columns put together. The elements in each group or family, have similar characteristics. Families have names rather than numbers. (Just like your family has a common last name.) Journal: March 22, 2010 Journal Prompt: Describe the following terms related to the periodic table of elements: Period Group Family Noble gases Groups…Here’s Where the Periodic Table Gets Useful!! Elements in Why?? the same • They have the same group have number of valence electrons. similar • They will form the chemical and same kinds of ions. physical properties!! (Mendeleev did that on purpose.) Hydrogen Hydrogen belongs to a family of its own. Hydrogen is a diatomic, reactive gas. Hydrogen was involved in the explosion of the Hindenberg. Hydrogen is promising as an alternative fuel source for automobiles Alkali Metals 1st column on the periodic table (Group 1) not including hydrogen. Very reactive metals, always combined with something else in nature (like in salt). Soft enough to cut with a butter knife Alkaline Earth Metals Second column on the periodic table. (Group 2) Reactive metals that are always combined with nonmetals in nature. Several of these elements are important mineral nutrients (such as Mg and Ca Transition Metals Elements in groups 3-12 Less reactive harder metals Includes metals used in jewelry and construction. Metals used “as metal.” Boron Family Elements in group 13 Aluminum metal was once rare and expensive, not a “disposable metal.” Carbon Family Elements in group 14 Contains elements important to life and computers. Carbon is the basis for an entire branch of chemistry. Silicon and Germanium are important semiconductors. Nitrogen Family Elements in group 15 Nitrogen makes up over ¾ of the atmosphere. Nitrogen and phosphorus are both important in living things. Most of the world’s nitrogen is not available to living things. The red stuff on the tip of matches is phosphorus. Oxygen Family or Chalcogens Elements in group 16 Oxygen is necessary for respiration. Many things that stink, contain sulfur (rotten eggs, garlic, skunks, etc.) Halogens Elements in group 17 Very reactive, volatile, diatomic, nonmetals Always found combined with other element in nature . Used as disinfectants and to strengthen teeth. The Noble Gases The Noble Gases Elements in group 18 VERY unreactive, monatomic gases Used in lighted “neon” signs Used in blimps to fix the Hindenberg problem. Have a full valence shell. The Atoms Family Story In the center of Matterville, there is a Name: place called the Nucleus Arcade, Patty Proton where two members of the Atoms Family like to hang out. Perky Patty Description: Proton, like her sisters, is quite large Positive with a huge smile and eyes that sparkle (+). Patty is always happy Favorite Activity: and has a very positive personality. Hanging out at the Nucleus Nerdy Nelda Neutron is large like Arcade Patty, but she has a boring, flat Name: mouth and eyes with zero expression (o). Her family is very apathetic and Nelda Neutron neutral about everything. Patty, Description: Nelda, and their sisters spend all their Neutral time at the arcade. Favorite Activity: Hanging out at the Nucleus Arcade Around the Nucleus Arcade, you will find a series of roadways that Name: are used by another member of the Elliott Electron Atoms Family, Enraged Elliott Description: Electron. Elliott races madly Negative around the Arcade on his bright Favorite Activity: red chrome-plated Harley- Racing around the arcade Davidson. He rides so fast that no one can be sure where he is at any time. Elliott is much smaller than Patty and Nelda and he is always angry because these bigger relatives will not let him in the Arcade. He has a frown on his face, eyes that are squinted with anger, and a very negative (-) attitude. The morale of Matterville is stable as long as each negative Electron brother is balanced out by one positive Proton sister. The number of residents in Matterville depends on the Proton and Neutron families. Challenge: What would happen to the morale of Matterville if one Elliott Electron was kidnapped? The first energy street can only hold only two Electron brothers. The second and third energy streets, called the Energy Freeway, can hold 8 brothers. The fourth energy street, called the Energy Superhighway, can hold 18 of the Energy brothers. Superhighway Can hold 18 electrons Energy Freeway Can hold 8 Energy electrons Freeway Can hold 8 electrons Nucleus Arcade Energy Street Contains protons & Can hold 2 neutrons electrons Valence Electrons Electrons that are involved in transfer or sharing. The number of valence electrons an element has increases from left to right across a period. Journal – 3/23/2010 Use the periodic to diagram elements O and Li. Remember that the electron configuration for each orbital is 2, 8, 8, 18. The Atoms Family - Atomic Math Challenge Atomic Number Symbol Name Atomic Mass ____________ or electrons Atomic number equals the number ofprotons ________________. protons neutrons Atomic mass equals the number of ______________ + __________ Assignment: Finish the rest of the worksheet and turn it in to your teacher. “Electron Cloud” Electrons are arranged around the Nucleus in SHELLS. For simplicity they can be thought of like mini-planets orbiting a central sun, but it is closer to the truth to think of them as "clouds" of electric charge around the Nucleus. Electron Dot Diagrams Examine the Electron Dot Diagram above – write at least 3 observations about the periodic table’s arrangement and how the arrangement compares to the number of dots it has beside it. Use the sciencesaurus book to help you write your observations page 265. Read page 268 – write 2 facts How to write and Electron Dot Diagram 1. Write the symbol of the element. (Each side of the letter represents an electron orbital.) Find the # of electrons in the C 2. valence shell (the outermost shell). 3. The dots representing the electrons in the valence shell are placed around the symbol beginning with the right side of the letter.
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