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Atoms and Bonding Big Idea and Essential Questions The atomic structure of an element determines how element interacts with other elements. Lesson 1 – The Atom: How do we know what parts make up the atom? Lesson 2 – The Periodic Table: How are elements arranged on the periodic table? Lesson 3 – Electrons and Chemical Bonding: How do atoms interact with each other? 1 Atoms and Bonding - Elements and Atoms The Building Blocks of Matter Matter may consist of elements, compounds, or mixtures. Compound: a pure substance made of 2 or more elements that are chemically combined. (Hydrogen and Oxygen: H2O) Elements: simple pure substances. Contains only 1 type of atom. Aluminum: Al Mixture: 2 or more substances that are not chemically combined. Sand, Gravel, Shells 2 Atoms and Bonding P158-159 What makes up matter? • The Greek philosopher Democritus thought matter could be divided into smaller units until you obtained a particle that could not be cut. • He called this particle atomos, meaning “not able to be divided.” • An atom is the smallest particle into which an element can be divided and still be the same element. • Scientists now know that atoms are made of even smaller particles, but the atom is the smallest unit that has the chemical properties of an element. • There are many types of atoms that combine in different ways to make all substances. 3 Atoms and Bonding 4 Atoms and Bonding - Elements and Atoms P160-161 Who developed the atomic theory? John Dalton (1808) thought that atoms were like smooth, hard spheres that could not be broken into smaller pieces. 5 Atoms and Bonding - Elements and Atoms P160-161 Who developed the atomic theory? J.J. Thomson (1897) suggested that atoms had negatively charged particles embedded in a positive sphere. 6 Atoms and Bonding - Elements and Atoms P160-161 Who developed the atomic theory? Ernest Rutherford (1908) Gold Foil Experiment led him to propose an atomic model with a positively charged nucleus - a small, dense center that has a positive charge. Electrons (negative) moved around a small, positively charged nucleus in the center of the atom. He named the positively charged particles Protons. 7 Atoms and Bonding - Elements and Atoms P160-161 Who developed the atomic theory? 8 Atoms and Bonding - Elements and Atoms P160-161 Atomic Theory and Models 9 Atoms and Bonding What is the current atomic theory? • In 1932, James Chadwick discovered that the nucleus contains uncharged particles called neutrons. • In the current atomic theory, electrons do not move in circular paths around the nucleus as Bohr thought. • Instead, the current theory suggests that electrons move within an area around the nucleus called the electron cloud. Atoms and Bonding Up and Atom! What are the parts of an atom? • Atoms are made up of protons, neutrons, and electrons. • Protons are the positively charged particles of atoms. The relative charge of a single proton is written as 1+. • In the unified atomic mass unit (u), the mass of a proton is about 1 u. Atoms and Bonding What are the parts of an atom? • Neutrons are particles that have no electrical charge. • The mass of a neutron is slightly more than that of a proton, but it is still close to 1 u. • Most atoms contain at least as many neutrons as protons. Atoms and Bonding What are the parts of an atom? • Together, protons and neutrons form the nucleus of the atom. • The overall charge of the nucleus is equal to the charge on the total number of protons in the nucleus. • The nucleus is small but very dense. Atoms and Bonding What are the parts of an atom? • The negatively charged particles of an atom are called electrons. The charge of a single electron is represented as 1-. • It is not possible to determine the exact position and speed of an electron at the same time. • So we picture the electrons as being in an electron cloud around the nucleus. Atoms and Bonding What are the parts of an atom? • Compared with protons and neutrons, electrons have very little mass. • The number of protons and electrons in an atom are the same, so their charges are balanced and the atom has an overall charge of 0. • An atom can gain or lose electrons to become an ion, which has a net positive or negative charge. Atoms and Bonding Parts of an atom Part of the atom Location Electric charge Relative mass Proton Nucleus 1+ Slightly less massive than a neutron Neutron Nucleus 0 Slightly more massive than a proton Electron Electron cloud 1- Almost 0 16 Atoms and Bonding Take a Number! How can we describe atoms? • Different combinations of protons, neutrons, and electrons produce atoms with different properties. • The number of each kind of particle within an atom determines its unique properties. • These different atoms combine to form the different substances all around us. • The number of protons distinguishes the atoms of one element from the atoms of another. • The number of protons in the nucleus of an atom is the atomic number of that atom. • The total number of protons and neutrons in an atom’s nucleus is its mass number. Atoms and Bonding How can we describe atoms? Atomic Number = # of Protons = # of electrons Atomic Mass = # of Protons + # of neutrons (Mass Number) 18 Atoms and Bonding How can we describe atoms? Unit 3 Lesson 1 The Atom Isotopes? • The atoms of a certain element always have the same number of protons, but the number of neutrons may differ. • Isotopes are atoms of the same element that have different numbers of neutrons. • The total number of protons and neutrons in an atom’s nucleus is its mass number. Atomic Mass – Average Mass of an element (decimal). Includes # of protons and neutrons and isotopes Atoms and Bonding How can we describe atoms? 20 Atoms and Bonding How can we describe atoms? 21 Atoms and Bonding How can we describe atoms? 22 Atoms and Bonding How can we describe atoms? 23 Atoms and Bonding The Atom WS Vital Statistics for Common Elements Element Protons Neutrons Hydrogen 1 0 Helium 2 Beryllium 2 4 Carbon 6 6 Nitrogen 7 7 Oxygen 8 Fluorine 9 11 8 10 Sodium 5 12 Electrons Atomic Number 1 2 1 Mass 1 2 4 4 4 9 6 7 8 9 11 6 7 8 12 9 19 11 23 14 16 24