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Matter & The Atom Matter The term matter describes all of the physical substances around us: your table, your body, a pencil, water, and so forth Matter Anything that has mass and takes up space (has volume) – Includes all things that can be seen, tasted, smelled, or touched – Does not include heat, sound, or light Matter is made of atoms Models Models are often used for things that are too small or too large to be observed or that are too difficult to be understood easily Models In the case of atoms, scientists use large models to explain something that is very small Models of the atom were used to explain data or facts that were gathered experimentally. So, these models are also theories Early Models of the Atom Democritus Universe was made of empty space and tiny bits of stuff Called these tiny bits of stuff atomos Atoms could not be divided Early Models of the Atom Lavoisier Demonstrated that burning wood caused no change in mass Law of Conservation of Matter Early Models of the Atom Dalton All elements are composed of indivisible particles. Atoms of the same element are the same Atoms of different elements are different. Compounds consisted of atoms of different elements combined together Early Models of the Atom Thomson Plum pudding model Atom made of a positively charged material with the negatively charged electrons scattered through it. Early Models of the Atom Rutherford Mostly empty space Small, positive nucleus Contained protons Negative electrons scattered around the outside Early Models of the Atom Bohr Electrons move in definite orbits around the nucleus Early Models of the Atom Chadwick Discovered the neutron Modern Model of the Atom The electron cloud Sometimes called the wave model Spherical cloud of varying density Varying density shows where an electron is more or less likely to be A closer look at quantum mechanics: http://www.fearofphysics.com/Atom/ atom1.html Atoms Family Album In the center of Matterville, there is a place called the Nucleus Arcade, where two members of the Atoms Family like to hang out. Perky Patty Proton, like her sisters, is quite large with a huge smile and eyes that sparkle (+). Patty is always happy and has a very positive personality. Nerdy Nelda Neutron is large like Patty, but she has a boring, flat mouth and eyes with zero expression (o). Her family is very apathetic and neutral about everything. Patty, Nelda, and their sisters spend all their time at the arcade. ++ Patty Proton Nelda Neutron Atoms Family Album Around the Nucleus Arcade, you will find a series of roadways that are used by another member of the Atoms Family, Enraged Elliott Electron. Elliott races madly around the Arcade on his bright red chrome plated HarleyDavidson. 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. Elliot Electron Atoms Family Album The first energy street can only hold only two Electron brothers. The second energy street, called the Energy Freeway, can hold 8 brothers. The third energy street, called the Energy Superhighway, can hold 18 of the brothers. Atomic Structure Nucleus – Protons – Neutrons Electrons Atomic Structure Electrons Tiny, very light particles Have a negative electrical charge (-) Move around the outside of the nucleus Atomic Structure Protons Much larger and heavier than electrons Protons have a positive charge (+) Located in the nucleus of the atom Atomic Structure Neutrons Large and heavy like protons Neutrons have no electrical charge Located in the nucleus of the atom Atomic Structure Describing Atoms Atomic Number = number of protons In a neutral atom, the # of protons = the # of electrons Describing Atoms Atomic Mass Number - equal to the number of protons plus neutrons. Describing Atoms Atomic Weight - average mass of the naturally occurring isotopes of an element .