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The Atom What is Matter? • anything that has ________ and takes up ________ • matter is made up of ________ (2 Volunteers) How Small are Atoms? • It would take a stack of about 50,000 aluminum atoms to equal the thickness of a sheet of aluminum foil from your kitchen • If you could enlarge a penny until it was as wide as the US, each of its atoms would be only about 3 cm in diameter – about the size of a ping pong ball • A human hair is about 1 million carbon atoms wide • A typical human cell contains roughly 1 trillion atoms • A speck of dust might contain 3x1012 (3 trillion) atoms • It would take you around 500 years to count the number of atoms in a grain of salt Activity: • Rip or cut a standard piece of paper in half as many times as you can. Class Discussion: • How many cuts were we able to make? ____ • Do you think we could keep cutting the paper forever? Why or why not? • You would have to cut the paper in half around thirty-one (31) times to get to the size of any atom. What is an Atom? • the smallest unit into which matter can be ____________________ • ___________________________ of all matter • comprised of a ________________(at it’s center) and an ___________________________ (surrounding the nucleus) • made up of ___________ _particles What are Subatomic Particles? • smaller than an atom • __________________ • __________________ • __________________ Early Atom Models: What is the Rutherford Model? • mostly empty • small, positively (+) charged nucleus • contained protons and electrons scattered around the outside Early Atom Models: What is the Bohr Model? • electrons (-) move in definite ___________ around the nucleus • Nucleus is made of ______________ (+) and ________________ (neutral). Modern Atom Model: What is the The Electron Cloud Model? • sometimes called the wave model • spherical cloud of varying density • varying density shows where an electron is more or less likely to be • The Bohr Model is still used to help explain characteristics of the atom. • ______________ charged particles (+) What are Protons? ++ + + + + + + - - - + - - • help make up the ___________ of the atom • equal to the _________________ of the atom • contribute to the _______________ • equal to the ___________ of ________________ in a neutral atom. What are Neutrons? - ++ + + + + + + - - - • ____________ particles; have no electric charge • help make up the nucleus of the atom • contribute to the _________ __________. What are Electrons? - - - • found _____________ the nucleus of the atom in the electron _____________. ++ + + + + + + - - • ______________ charged particles (-) - • each orbital/level can hold a maximum number of electrons • 1st orbital = _________ • 2nd orbital = _________ • 3rd orbital = _________ What are Electrons? - ++ + + + + + + - - - • move so rapidly around the nucleus that they create an _____________________ - • mass is insignificant when compared to protons and neutrons • equal to the _________ of _____________________ in a neutral atom • involved in the formation of chemical bonds What are Valence • found in the outermost energy level of the Electrons? electron cloud (called the ______________) • involved in bonding • determine the chemical properties of an element How is the Atom’s Center Formed? Protons and neutrons are grouped together to form the “center” or ________________ of an atom Notice that the electrons are not a part of the nucleus - - + - + + - Atomic Structure How are Atoms Described? The Atomic Symbol: • atomic number = ________________ • in a _____________ atom, the # of protons = the # of electrons • atomic mass= _________________ + _________________ • the number of protons in the nucleus of an atom What is Atomic Number? - - + ++ - What would be the atomic number of this atom? What is the Atomic Mass? • the total number of protons and neutrons in an atom’s nucleus • expressed in Atomic Mass Units (amu) – each proton or neutron has a mass of 1 amu What would be the atomic mass of this atom? + - 3 + ++ 4 3 protons + 4 neutrons = an atomic mass of 7 amu Why did we not account for the electrons when calculating the mass number? - - Hydrogen (H) Atom • Let’s use the Bohr Model to sketch a hydrogen atom. • notice the one electron in the first orbital P = Atomic # = E=P= N = Atomic Mass – Atomic # = Oxygen (O) Atom • notice the two electrons in the first orbital/level and the six in the second Bohr Diagram P = Atomic # ________ E=P ________ N = Atomic Mass – Atomic # ________ Sodium (Na) Atom • notice the two electrons in the first orbital/level, eight in the second, and one in the third Bohr Diagram P= E= N=