Chapter 02 (The Structure of the Atom and the Periodic Table).pdf

Because learning changes everything.® GENERAL, ORGANIC, AND 11TH Edition BIOCHEMISTRY...

Because learning changes everything.® GENERAL, ORGANIC, AND 11TH Edition BIOCHEMISTRY Katherine J. Denniston Danaè R. Quirk Joseph J. Topping Robert L. Caret Chapter 2 The Structure of the Atom and the Periodic Table © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  2.1 Composition of the Atom Atom - the basic structural unit of an element. The smallest unit of an element that retains the chemical properties of that element. © McGraw Hill LLC  Electrons, Protons, and Neutrons Atoms consist of three primary particles: protons neutrons electrons Loading… Nucleus - small, dense, positively charged region in the center of the atom containing: protons - positively charged particles. neutrons - uncharged particles. © McGraw Hill LLC  Characteristics of Atomic Particles Electrons: negatively charged particles located outside of the nucleus of an atom: move very rapidly in a relatively large volume of space while the nucleus is small and dense. Protons and electrons have charges that are equal in magnitude but opposite in sign. A neutral atom (no electrical charge) has the same number of protons and electrons. © McGraw Hill LLC  Selected Properties of the Three Basic Subatomic Particles Loading… E -5 © McGraw Hill LLC  Symbolic Representation of an Element Atomic&A A = Mass Number Z = Atomic X X = Elemental Symbol Number Z Atomic number (Z) - the number of protons in the atom. Mass number (A) - sum of the number of protons and neutrons. © McGraw Hill LLC  Atomic Calculations mass number = number of protons + number of neutrons * 2 number of neutrons = mass number − number of protons number of neutrons = mass number − atomic number number of neutrons = A − Z © McGraw Hill LLC  Determining the Composition of an Atom Calculate the number of protons, neutrons, and electrons in each of the following: "B E © McGraw Hill LLC  Isotopes Isotopes - atoms of the same element having different masses: contain same number of protons. contain different numbers of neutrons. A = %XA + © McGraw Hill LLC  Isotopic Calculations Isotopes of the same element have identical chemical properties. Some isotopes are radioactive. Find chlorine on the periodic table. What is the atomic number of chlorine? 17 What is the mass given? 35.45 This is not the mass number of an isotope. © McGraw Hill LLC 1  Atomic Mass What is this number, 35.34? The atomic mass - the weighted average of the masses of all the isotopes that make up chlorine: Loading… Chlorine consists of chlorine-35 and chlorine-37 in a 3:1 ratio. Weighted average is an average corrected by the relative amounts of each isotope present in nature. © McGraw Hill LLC 1  Determining Atomic Mass 1 Calculate the atomic mass of naturally occurring chlorine if 75.77% of chlorine atoms are and 24.23% of chlorine atoms are Step 1: Convert the percentage to a decimal fraction. © McGraw Hill LLC 1  Determining Atomic Mass 2 Step 2: Multiply the decimal fraction by the mass of that isotope to determine the contribution of each isotope. For 0.7577 × 35.0 amu = 26.5 amu For t 0.2423 × 37.0 amu = 8.97 amu Step 3: Add the mass contributed by each isotope 26.52 amu + 8.965 amu = 35.5 amu © McGraw Hill LLC 1  Atomic Mass Determination Neon has three naturally occurring isotopes. Column 1 has no header and notes neon's three naturally occurring isotopes for mass and abundance. What is the atomic mass of neon? © McGraw Hill LLC 1  2.4 The Periodic Law and the Periodic Table Dmitri Mendeleev and Lothar Meyer - independently developed the precursor to our modern Periodic Table: They noticed that as you list elements in order of atomic mass, there is a distinct regular variation of their properties. Periodic Law - the physical and chemical properties of the elements are periodic functions of their atomic numbers. © McGraw Hill LLC 1  Classification of the Elements Access the text alternative for slide images. © McGraw Hill LLC 1  Parts of the Periodic Table Period – a horizontal row of elements. They contain 2, 8, 8, 18, 18, 32, and 32 elements. A Group – (also called families) column of elements : B Elements in a particular group or family share many similarities, as in a human family. © McGraw Hill LLC 1  Category Classification of Elements Metals - elements that tend to lose electrons during a chemical change. Nonmetals – elements that tend to gain electrons during a chemical change. Metalloids - have properties intermediate between metals and nonmetals. © McGraw Hill LLC 1  Metals Metals: A substance whose atoms tend to lose electrons during chemical change. Elements found primarily in the left of the periodic table. Properties: High thermal and electrical conductivities. High malleability and ductility. Metallic luster. Solid at room temperature. © McGraw Hill LLC 1  Nonmetals Nonmetals: A substance whose atoms may gain electrons, forming negative ions. Elements found in the right of the periodic table. Properties: Brittle. Powdery solids or gases. Opposite of metal properties. © McGraw Hill LLC 2  Using the Periodic Table Identify the group and period to which each of the following belongs: a. P b. Cr page 16 c. Element 30 How many elements are found in period 6? How many elements are in group 15 (or VA)? © McGraw Hill LLC 2  2.5 Electron Arrangement and the Periodic Table The electron arrangement is the primary factor in understanding how atoms join together to form compounds. Electron configuration - describes the arrangement of electrons in atoms. © McGraw Hill LLC 2  The Quantum Mechanical Atom Bohr’s model of the hydrogen atom did not clearly explain the electron structure of other atoms: Electrons in very specific locations, principal energy levels. Wave properties of electrons conflict with specific location. Schröedinger developed equations that took Min into account the particle nature and the wave nature of the electrons. © McGraw Hill LLC 2  Schröedinger’s equations Equations that determine the probability of finding an electron in specific region in space, quantum mechanics: ~ Principal energy levels n ( = , 2 ,3 ). Each energy level has one or more sublevels ~ or subshells (s, p, d, f). ~ Each sublevel contains one or more atomic orbitals. © McGraw Hill LLC 2  Principal Energy Levels Regions where electrons may be found Have values designated as n = 1 2 , ,....... The larger the value of n, the higher the energy level and the farther away from the nucleus the electrons are. The number of sublevels in a principal energy level is equal to n: in n = 1, there is one sublevel. in n = 2, there are two sublevels. © McGraw Hill LLC 2  Electrons in Principal Energy Levels The electron capacity of a principal energy levelP- 2 (or total electrons it can hold) is: =1 > 2 - 2n n 5 => 50 n = n = 1 can hold = 2 electrons. n = 2 can hold = 8 electrons. How many electrons can be in the n = 3 level? = 18 © McGraw Hill LLC 2  Sublevels Sublevel: a set of energy-equal orbitals within a principal energy level. Subshells increase in energy: s