Chapter 3Atoms and Elements Classification of Matter Copyright © 2009 by Pearson Education, Inc.

Matter Matter is the “stuff” that makes up all things. 2 Copyright © 2009 by Pearson Education, Inc.

Pure Substances A pure substance is 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. 3

Elements Elements are pure substances that contains atoms of only one type. Copper, Cu Lead, Pb Aluminum, Al 4 Copyright © 2009 by Pearson Education, Inc.

Compounds contain two or more elements in a definite ratio. Salt (NaCl) Table sugar (C 12 H 22 O 11 ) Water (H 2 O) 5 Copyright © 2009 by Pearson Education, Inc.

Elements in a Compound “Table salt” is a compound that contains the elements sodium and chlorine. 6

Mixtures A mixture is a type of matter that consists 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. 7

Physical Separation of a Mixture Example: Pasta and water are separated with a strainer. 8 Copyright © 2009 by Pearson Education, Inc.

Homogeneous Mixtures In a homogeneous mixture, the composition is uniform throughout. the different parts of the mixture are not visible. 9 Copyright © 2009 by Pearson Education, Inc.

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. 10 Copyright © 2009 by Pearson Education, Inc.

Classification of Matter 11

Learning Check Identify each of the following as a pure substance or a mixture. A. pasta and tomato sauce B. aluminum foil C. helium D. air 12

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 13

Chapter 3Atoms and Elements 3.2 Elements and Symbols 14 Copyright © 2009 by Pearson Education, Inc.

Elements Elements are pure substances that cannot be separated into simpler substances by ordinary laboratory processes. the building blocks of matter. gold carbon aluminum 15

Sources of Some Element Names Some elements are named for planets, mythological figures, minerals, colors, scientists, and places. 16

Symbols of Elements A symbol represents the name of an element. consists of 1 or 2 letters. starts with a capital letter. 1-Letter Symbols 2-Letter Symbols C carbon Co cobalt N nitrogenCa calcium F fluorine Al aluminum O oxygen Mg magnesium 17

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) 18 Copyright © 2009 by Pearson Education, Inc.

Physical Properties of Elements The physical properties of an element are observed or measured without changing its identity. include the following: Shape Density ColorMelting point Odor and tasteBoiling point 19

Physical Properties of Elements Some physical properties of copper are: ColorRed-orange LusterVery shiny Melting point1083 °C Boiling point2567 °C Conduction of electricityExcellent Conduction of heatExcellent 20 Copyright © 2009 by Pearson Education, Inc.

Learning Check Select the correct symbol for each. A. Calcium 1) C2) Ca3) CA B. Sulfur 1) S2) Sl3) Su C. Iron 1) Ir2) FE3) Fe 21

Learning Check Select the correct name for each symbol. A. N 1) neon 2) nitrogen 3) nickel B. P 1) potassium 2) phlogiston3) phosphorus C. Ag 1) silver 2) agean3) gold 22

Chapter 3 Atoms and Elements 3.3 The Periodic Table 23 Copyright © 2009 by Pearson Education, Inc.

Groups and Periods On the periodic table, elements are arranged according to similar properties. groups contain elements with similar properties in vertical columns. periods are horizontal rows of elements. 24

Groups and Periods 25 Copyright © 2009 by Pearson Education, Inc.

Periodic Table 26

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. 27

Names of Some Representative Elements 28

Alkali Metals Group 1A (1), the alkali metals, includes lithium, sodium, and potassium. 29 Copyright © 2009 by Pearson Education, Inc.

Halogens Group 7A (17), the halogens, includes chlorine, bromine, and iodine. 30 Copyright © 2009 by Pearson Education, Inc.

Learning Check Identify the element described by the following: A. Group 7A (17), Period 4 1) Br2) Cl3) Mn B. Group 2A (2), Period 3 1) beryllium2) boron 3) magnesium C. Group 5A (15), Period 2 1) phosphorus 2) arsenic3) nitrogen 31

Metals, Nonmetals, and Metalloids The heavy zigzag line separates metals and nonmetals. Metals are located to the left. Nonmetals are located to the right. Metalloids are located along the heavy zigzag line between the metals and nonmetals. 32

Metals, Nonmetals, and Metalloids on the Periodic Table 33

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. 34

Comparing a Metal, Metalloid, and Nonmetal 35

Learning Check Identify each of the following elements as 1) metal, 2) nonmetal, or 3) metalloid. A. sodium____ B. chlorine____ C. silicon ____ D. iron____ E. carbon____ 36

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, P3) N, P, As, Sb C. Metalloids in Group 4A (14) 1) C, Si, Ge, 2) Si, Ge 3) Si, Ge, Sn, Pb 37

38 Chapter 3 Atoms and Elements 3.4 The Atom Copyright © 2009 by Pearson Education, Inc.

39 Dalton’s Atomic Theory In Dalton’s atomic theory, atoms are tiny particles of matter. of an element are similar and different from other elements. of two or more different elements combine to form compounds. are rearranged to form new combinations in a chemical reaction.

40 Subatomic Particles Atoms contain subatomic particles. Protons have a positive (+) charge. Electrons have a negative (-) charge. Neutrons are neutral. Like charges repel and unlike charges attract.

Electrons Thomson- Found that cathode ray consists of tiny, negatively charged particles called electrons. Electrons are emitted from electrodes made of two thin pieces of metal Many different metals may be used to make electrodes Different metals contain different electrons Cathode rays can be deflected by bringing either a magnet or an electrically charged plate near tube. This deflection depends on the strength of deflecting magnetic or electric field the size of the negative charge on the electron the mass of electron

Electron

43 Rutherford’s Gold Foil Experiment In Rutherford’s gold foil experiment, positively charged particles were aimed at atoms of gold. mostly went straight through the atoms. were deflected only occasionally. Conclusion: There must be a small, dense, positively charged nucleus in the atom that deflects positive particles that come close.

44 Rutherford’s Gold Foil Experiment Copyright © 2009 by Pearson Education, Inc.

45 Structure of the Atom An atom consists of a nucleus that contains protons and neutrons. of electrons in a large, empty space around the nucleus. Copyright © 2009 by Pearson Education, Inc.

46 Atomic Mass Scale On the atomic mass scale, 1 atomic mass unit (amu) has a mass equal to 1/12 of the mass of the carbon-12 atom. a proton has a mass of about 1 (1.007) amu. a neutron has a mass of about 1 (1.008) amu. an electron has a very small mass, amu.

47 Particles in the Atom

48 Learning Check Identify each statement as describing a 1) proton, 2) neutron, or 3) electron. A. found outside the nucleus B. has a positive charge C. is neutral D. found in the nucleus

Learning Check Is each of the following statements true or false? Protons are heavier than electrons Protons are attracted to neutrons Electrons are small that they have no electrical charge The nucleus contains all the protons and neutrons of an atom 49

Chapter 3 Atoms and Elements Atomic Number and Mass Number Copyright © 2009 by Pearson Education, Inc.

51 The atomic number is specific for each element. is the same for all atoms of an element. is equal to the number of protons in an atom. appears above the symbol of an element. Atomic Number 11 Na Atomic Number Symbol

52 Examples of atomic number and number of protons: Hydrogen has atomic number 1; every H atom has one proton. Carbon has atomic number 6; every C atom has six protons. Copper has atomic number 29; every Cu atom has 29 protons. Gold has atomic number 79; every Au atom has 79 protons. Atomic Number and Protons

53 State the number of protons in each. A. A nitrogen atom 1) 5 protons 2) 7 protons 3) 14 protons B. A sulfur atom 1) 32 protons 2) 16 protons 3) 6 protons C. A barium atom 1) 137 protons 2) 81 protons 3) 56 protons Learning Check

54 An atom of an element is electrically neutral; the net charge of an atom is zero. has an equal number of protons and electrons. number of protons = number of electrons Aluminum has 13 protons and 13 electrons. The net (overall) charge is zero. 13 protons (13+) + 13 electrons (13 -) = 0 Electrons in An Atom

55 Mass Number The mass number represents the number of particles in the nucleus. is equal to the number of protons + the number of neutrons.

56 Atomic Models

57 Number of protons = Atomic number Number of protons + neutrons = Mass number Number of neutrons = mass number – atomic number (protons) Note: Mass number is given for specific isotopes only. Study Tip: Protons and Neutrons

58 An atom of zinc has a mass number of 65. A. How many protons are in this zinc atom? 1) 302) 353) 65 B. How many neutrons are in the zinc atom? 1) 302) 353) 65 C. What is the mass number of a zinc atom that has 37 neutrons? 1) 372) 653) 67 Learning Check

59 An atom has 14 protons and 20 neutrons. A. Its atomic number is 1) 142) 163) 34 B. Its mass number is 1) 142) 163) 34 C. The element is 1) Si2) Ca3) Se Learning Check