Chapter 3 Atoms and Elements 3.1 Classification of Matter
Matter Matter is the “stuff” that makes up all things.
Pure Substances A pure substanceis classified as • matter with a specific composition. • an element when composed of one type of atom. • a compound when composed of two or more elements combined in a definite ratio.
Elements Elements are • pure substances that contains atoms of only one type. Copper, Cu Lead, Pb Aluminum, Al
Compounds Compounds • contain two or more elements in a definite ratio. Salt (NaCl) Table sugar (C12H22O11) Water (H2O)
Elements in a Compound “Table salt” is a compound that contains the elements sodium and chlorine.
Mixtures A mixtureis a type of matter thatconsists of • two or more substances that are physically mixed, not chemically combined. • two or more substances in different proportions. • substances that can be separated by physical methods.
Physical Separation of a Mixture Example: Pasta and water are separated with a strainer.
Homogeneous Mixtures In a homogeneous mixture, • the composition is uniform throughout. • the different parts of the mixture are not visible.
Heterogeneous Mixtures In a heterogeneous mixture, • the composition of substances is not uniform. • the composition varies from one part of the mixture to another. • the different parts of the mixture are visible.
Example Identify each of the following as a pure substance or a mixture. A. pasta and tomato sauce B. aluminum foil C. helium D. air
Learning Check Identify each of the following as a homogeneous or heterogeneous mixture: A. hot fudge sundae B. air C. sugar water D. peach pie
Chapter 3 Atoms and Elements 3.2 Elements and Symbols
Elements Elementsare • pure substances that cannot be separated into simpler substances by ordinary laboratory processes. • the building blocks of matter. gold carbon aluminum
Sources of Some Element Names Some elements are named for planets, mythological figures, minerals, colors, scientists, and places.
Symbols of Elements Asymbol • represents the name of an element. • consists of 1 or 2 letters. • starts with a capital letter. 1-Letter Symbols2-Letter Symbols C carbon Co cobalt N nitrogen Ca calcium F fluorine Al aluminum O oxygen Mg magnesium
Symbols from Latin Names Several symbols are derived from Latin names as shown below. Cu, copper (cuprum) Au, gold (aurum) Fe, iron (ferrum) Ag, silver (argentum)
Physical Properties of Elements The physical properties of an element • are observed or measured without changing its identity. • include the following: Shape Density Color Melting point Odor and taste Boiling point
Physical Properties of Elements Some physical properties of copper are: Color Red-orange Luster Very shiny Melting point 1083 °C Boiling point 2567 °C Conduction of electricity Excellent Conduction of heat Excellent
Example Select the correct symbol for each. A. Phosphorous 1) K 2) P 3) Ph B. Aluminum 1) Al 2) Au 3) An C. Iron 1) Ir 2) FE 3) Fe
Learning Check Select the correct name for each symbol. A. Ne 1) neon 2) nitrogen 3) nickel B. K 1) potassium 2) phlogiston 3) phosphorus C. Au 1) silver 2) agean 3) gold
Chapter 3 Atoms and Elements 3.3 The Periodic Table
Development of the Periodic Table Mendeleev’s Periodic Table (1871) Until the discovery of the proton, the elements were typically organized by increasing atomic weight. The modern organization is by increasing atomic number.
Groups and Periods On the periodic table, • elements are arranged according to similar properties. • groupscontain elements with similar properties in vertical columns. • periods are horizontal rows of elements.
Periods: 7 horizontal rows. • Groups: 18 vertical columns. • International standard: 1-18 • US system: 1A-8A, 1B-8B
Group Numbers Group Numbers • use the letter A for the representative elements (1A to 8A) and the letter B for the transition elements. • also use numbers 1-18 to the columns from left to right.
Alkali Metals Group 1A (1), the alkali metals,includes lithium, sodium, and potassium.
Halogens Group 7A (17), the halogens, includes chlorine, bromine, and iodine.
Examples Identify the element described by the following: A. Group 7A (17), Period 4 1) Br 2) Cl 3) Mn B. Group 2A (2), Period 3 1) beryllium 2) boron 3) magnesium C. Group 5A (15), Period 2 1) phosphorus 2) arsenic 3) nitrogen
Metals, Nonmetals, and Metalloids The heavy zigzag line separates metals and nonmetals. • Metals are located to the left. • Nonmetalsare located to the right. • Metalloidsare located along the heavy zigzag line between the metals and nonmetals.
Properties of Metals, Nonmetals, and Metalloids Metals • are shiny and ductile. • are good conductors of heat and electricity. Nonmetals • are dull, brittle, and poor conductors. • are good insulators. Metalloids • are better conductors than nonmetals, but not as good as metals. • are used as semiconductors and insulators.
Examples Identify each of the following elements as 1) metal, 2) nonmetal, or 3) metalloid. A. sodium ____ B. iodine ____ C. Argon ____ D. iron ____ E. Silicon ____
Learning Check Match the elements to the description. A. Metals in Group 4A (14) 1) Sn, Pb 2) C, Si 3) C, Si, Ge, Sn B. Nonmetals in Group 5A (15) 1) As, Sb, Bi 2) N, P 3) N, P, As, Sb C. Metalloids in Group 4A (14) 1) C, Si, Ge, 2) Si, Ge 3) Si, Ge, Sn, Pb