Module 6 Lesson 1 Matter By: Rasha Shawky Chemistry is the study of matter, its composition and properties. What makes up matter? • Scientists have come to agree that matter is made up of small particles, and they use the term atom to describe them. What makes up matter? • An atom is the building block of matter. • 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. What makes up matter? • There are many types of atoms that combine in different ways to make all substances. What are the parts of an atom? • Atoms are made up of protons, neutrons, and electrons. • Protons are the positively charged particles of atoms. p+. • Neutrons are particles that have no electrical charge. n° • Together, protons and neutrons form the nucleus of the atom. • The nucleus is small but very dense. • The negatively charged particles of an atom are called electrons. e-. • 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. What are the parts of an atom? • 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. What are the parts of an atom? Particle Charge Proton +1 Neutron No charge Electron -1 • Identify the parts of the atom. How can we describe atoms? • 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. What are the parts of an atom? • An atom can gain or lose electrons to become an ion, which has a net positive or negative charge. Elements • An element is a type of matter made of just one kind of atom. • Elements are pure substances that cannot be broken into simpler substances. Elements • All atoms of an element have the same number of protons. • For example, boron is an element. Boron Every atom of boron contains exactly five protons. • No other element has atoms with exactly five protons. Examples of elements include neon, mercury, chlorine, silver, and copper. • Carbon How are the elements arranged on the periodic table? • Each vertical column of elements on the periodic table is called a group. • Each horizontal row of elements on the periodic table is called a period. Why is it called the periodic table? • Because elements f the same group have similar chemical and physical properties. Copyright © Houghton Mifflin Harcourt Publishing Company Making Arrangements What information is contained in each square on the periodic table? • Each square contains an element’s chemical name, atomic number, chemical symbol, and average atomic mass. • The atomic number is placed at the top of each square. • A compound is a pure substance formed when two or more elements combine. • The properties of a compound are often different from the properties of the elements that form it. • For example, atoms of carbon and oxygen will react, forming the compound carbon dioxide. • This compound has its own properties that are different than those of carbon or oxygen. Putting It All Together • Which substances are elements? Which substances are compounds? How do atoms join together? • A huge variety of substances are possible because atoms join together by forming chemical bonds. • A chemical bond is a farce that holds atoms or ions together. • A group of atoms that are held together by chemical bonds is called a molecule. Copyright © Houghton Mifflin Harcourt Publishing Company Ionic Bond • An ionic bond is a force of attraction between oppositely charged ions. • Ionic bonds form when electrons are transferred from a metal atom to a nonmetal atom. • In the process of ionic bonding, valence electrons move from the outer shell of the metal atom to the outer shell of the nonmetal atom. Copyright © Houghton Mifflin Harcourt Publishing Company Ionic Bond Covalent bond • A covalent bond forms when atoms share one or more pairs of electrons. • When two nonmetal atoms bond, a large amount of energy is needed for either atom to lose an electron. So they bond by sharing electrons. • In a covalent bond, the shared electrons fill empty spaces in the outermost electron shell of each atom. Covalent bond What is a molecule? • Substances that have covalent bonds are made of individual particles called molecules. • A molecule is a group of atoms held together by chemical bonds. • A molecule is the smallest unit of a compound that can be identified as that compound. What is a molecule? • In a water molecule, two hydrogen atoms form covalent bonds with a central oxygen atom.
