Chapter 4: Elements and Symbols PDF

Lecture Presentation Chapter 4 Elements and Symbols...

Lecture Presentation Chapter 4 Elements and Symbols Karen C. Timberlake General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Concept Map General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  4.1 Elements and Symbols Elements are pure substances from which all other things are built. cannot be broken down into simpler substances. are listed on the inside carbon front cover of this text. Element names come from the Latin name, planets, mythological figures, minerals, colors, geographic locations, and famous people. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Chemical Symbols Chemical symbols represent the names of the elements. consist of one to two letters and start with a capital letter. often derived from the Latin name. One-Letter Symbols Two-Letter Symbols C carbon Co cobalt N nitrogen Ca calcium F fluorine Al aluminum O oxygen Mg magnesium General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Names and Symbols of Common Elements General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Study Check Write the correct chemical symbols for each of the following elements: A. iodine B. iron C. magnesium D. zinc E. nitrogen General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Study Check Give the names of the elements with the following compounds: A. PO5 B. Al(OH)3 C. MnBr D. NH4Cl E. K3PO4 General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Periodic Table Periodic Table of the Elements Discovered by Dmitri Mendeleev in 1872. Elements are arranged according to properties. Groups (family) contain elements with similar properties in vertical columns. Periods are horizontal rows of elements, counted from top to bottom of the table as Periods 1−7. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Periodic Table of Elements General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Group Numbers Group numbers are written at the top of each vertical column. Use the letter A for representative elements/main group elements (Groups 1A–8A). Use the letter B for transition elements (Groups 3B–12B). An alternative system uses numbers of 1–18 for all of the groups, from left to right, across the periodic table. Because both systems are currently in use, they are both shown on the periodic table in this text and are included in our discussions of elements and group numbers. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake Elongated Periodic Table General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Groups and Periods Determine what element is in Group 2, Period 4. Vertical columns represent groups of elements, and horizontal rows represent periods. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  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. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Metals, Nonmetals, and Metalloids Metals, except for hydrogen, located on the left of the periodic table, are shiny and ductile, and conduct heat and electricity. are solids, except for mercury (Hg), which is a liquid. In chemical reactions, they tend to transfer their electrons. Nonmetals, located on the right side of the periodic table, are dull, brittle, and poor conductors but often good insulators. have low densities and melting points. In chemical reactions, they tend to accept and/or share electrons. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Metals, Nonmetals, and Metalloids Metalloids, located along the heavy zigzag line on the periodic table, exhibit properties of both metals and nonmetals. are better conductors than nonmetals but not as good as metals. are used as semiconductors and insulators, because they can be modified to function as conductors or insulators. Silicon, for example, is a semiconductor; it does not conduct electricity under certain applied voltages, but becomes a conductor at higher applied voltages. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Group Names Periodicity (Periodic Trends) is where the elements have similar properties in a group/family and those properties vary in a fairly regular/predictable way as we go up or down a group. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Alkali Metals Alkali Metals Group 1A (1): Softness (ability to cut with knife) increases down group. Violence of reaction with water increases down group Low energy so easily gives up an electron to become an ion with a +1 charge. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Alkaline Earth Metals Sr gives the red color in fireworks. Alkaline Earth Metals Group 2A (2) elements, the alkaline earth metals, are shiny but not as reactive as Group 1A metals. beryllium (Be) magnesium (Mg) calcium (Ca) strontium (Sr) barium (Ba) radium (Ra) Can become ion with +2 charge. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Halogens & Noble Gases Halogens Noble Gases Group 7A (17), the Group 8A (18), the includes the following: includes the following: fluorine (F) helium (He) chlorine (Cl) neon (Ne) bromine (Br) argon (Ar) iodine (I) krypton (Kr) Highly reactive xenon (Xe) Can become ion with a - radon (Rn) 1 charge. Highly unreactive/stable Has 8 valence e- General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Study Check Identify each of the following elements as a metal, a nonmetal, or a metalloid: A. sodium B. chlorine C. silicon D. iron E. carbon General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Chemistry Link to Health: Elements Essential to Health Of all the elements, 20 are essential for the well-being and survival of the human body. four—oxygen, carbon, hydrogen, and nitrogen—make up 96% of our body mass. most of our hydrogen and oxygen is found as water, which makes up 55 to 60% of our body mass. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Chemistry Link to Health: Elements Essential to Health General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Dalton’s Atomic Theory John Dalton (1766-1844) developed a model to explain matter and how it interacts. In Dalton’s atomic theory, atoms are tiny particles of matter. of an element are similar to each other but different from those of other elements. of two or more different elements combine to form compounds. are can rearrange, separate or combine to form new substances in a chemical reaction. Atoms are never created or destroyed during a chemical reaction. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  The Atom Atom the smallest particle of an element that retains the characteristics of that element. The atom is made up of three subatomic particles Proton Electron Neutron General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Electrical Charges in an Atom Atoms contain the following subatomic particles: protons that have a positive (+) charge electrons that have a negative (–) charge neutrons that have no charge (neutral) Like charges repel and unlike charges attract. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Discoveries of e- and p+ From his experiment, J. J. Thomson realized that cathode rays contain negatively charged particles. particles (now called electrons) have a much smaller mass than the atom. Thomson’s student, Ernest Rutherford, conducted his gold foil experiment and discovered that the atom had a concentrated positively charged (protons) center that he called nucleus. a center that contained most of the atom’s mass. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Structure of the Atom In an atom, the protons and neutrons that make up almost all the mass are packed into the tiny volume of the nucleus. The rapidly moving electrons (negative charge) surround the nucleus and account for the large volume of the atom. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Mass of the Atom Because the mass of subatomic particles is so small, chemists use a very small unit of mass called the atomic mass unit (amu). 1 amu has a mass equal to 1/12 of the mass of the carbon-12 atom that contains six protons and six neutrons. 1 amu = 1 Dalton (Da) in biology. Electrons have such a small mass that they are generally not included in the mass of an atom. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Subatomic Particles in the Atom Subatomic particles have a very small mass, and an electron has a mass that is much less than that of a proton or a neutron. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Study Check Which of the following subatomic particles fits each of the descriptions below? protons, neutrons, or electrons A. found outside the nucleus B. have a positive charge C. have mass but no charge General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Atomic Number The atomic number (Z) defines the element. is a whole number 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 in the periodic table. Atomic number = number of protons Atomic number 11 Symbol General, Organic, and Biological Chemistry: Structures of Life, 5/e Na © 2016 Pearson Education, Inc. Karen C. Timberlake  Atomic Number = Protons in an Atom All atoms of lithium (left) contain three protons, and all atoms of carbon (right) contain six protons. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Atoms are Neutral Atoms are neutral and have a net charge of zero. number of protons = number of electrons Aluminum has 13 protons and 13 electrons. The net (overall) charge is zero. 13 protons (+1) + 13 electrons (-1) = 0 General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Mass Number The mass number (A) represents the number of particles in the nucleus. is equal to the number of protons + the number of neutrons. is always a whole number. does not appear in the periodic table. Mass number = number of protons + number of neutrons General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Study Check An atom of lead (Pb) has a mass number of 207. A. How many protons are in the nucleus? B. How many neutrons are in the nucleus? C. How many electrons are in the atom? General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Isotopes Isotopes are atoms of the same element. have different mass numbers. have the same number of protons but different numbers of neutrons. can be distinguished by their atomic symbols. To name the isotope write the element followed by the mass number; magnesium-24 or Mg-24 General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Study Check Naturally occurring carbon consists of three isotopes: 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of the three isotopes. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Study Check 1. Which of the pairs below are isotopes of the same element? 2. In which of the pairs below do both atoms have eight neutrons? 15 15 A. 8 X 7 X 12 14 B. 6 X 6 X 15 16 C. 7 X 8 X General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Calculating Atomic Mass Atomic mass is the weighted average of all naturally occurring isotopes of that element. number on the periodic table below the chemical symbol. Chlorine, with two naturally occurring isotopes, has an atomic mass of 35.45 amu (although no individual Cl atom actually has this mass). General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Calculating Atomic Mass To calculate atomic mass (using chlorine as an example), use experimental data for both isotopes. Atomic mass of Mg = 18.88 amu + 2.531 amu + 2.902 amu = 24.31 amu (weighted average mass) General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Study Check Lithium consists of two naturally occurring isotopes, 6Li and 7Li. Which isotope is the more prevalent one? (According to the periodic table, the atomic mass of lithium is 6.941 amu.) General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  4.6 Electron Energy Levels Just like when sunlight passes through water droplets to separate the colors to form a rainbow, when light from a heated element passes through a prism, it separates into distinct lines of color separated by dark areas producing an atomic spectrum. Each element has its own unique atomic spectrum. Learning Goal Describe the energy levels, sublevels, and orbitals for the electrons in an atom. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Electron Energy Levels The lines in an atomic spectrum are associated with the changes in energies of the electrons. In an atom, each electron has a specific energy, known as its energy level, which is assigned principal quantum numbers (n) = (n = 1, n = 2, …). increases in energy as the value of n increases and electrons are farther away from the nucleus. The energy of an electron is quantized—electrons can have only specific energy values. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Quantized Energy Levels The energy of electrons in an atom is quantized, which means that an electron in an atom can have only certain allowed energies (think of a bookcase, or rungs of a ladder). Electrons with the same energy are grouped in the same energy level (n). The lowest possible energy An electron can have only the level is the ground state energy of one of the energy (n=1). levels in an atom. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Changes in Electron Energy Level Electrons move to a higher energy level when they absorb energy. When electrons fall back to a lower energy level, energy is emitted. If that energy is in the visible spectrum, we can see it as a color. The energy emitted or absorbed is equal to the differences between the two energy levels. General, Organic, and Biological Chemistry: Structures of Life, 5/e © 2016 Pearson Education, Inc. Karen C. Timberlake  Sublevels (s,p,d,f) Each energy level consists of one or more sublevels. The number of sublevels in an energy level is equal to the principal quantum number n of that energy level. The sublevels are identified as s, p, d, and f. The order of sublevels in an energy level is s