Lecture 2: Atoms and Elements Lecture Outline Defining matter and its types Elements and symbols The periodic table The atom Atomic number and mass number Isotopes and atomic mass Electron energy levels Electron configuration Periodic trends (as in before, group activity takes center and front in the lecture)

Defining Matter and its types Matter: Matter is stuff. it is what makes up a substance. Matter makes things we see everyday such as water, wood, cooking pan, clothes, shoes, etc.

Properties of Matter Type of Properties Physical Chemical Obtained without changing identity (No color, shape, taste, or density change) Chemical Obtained by changing identity (New color, shape, taste, etc) Chemical Change Change in which new substances are formed by changing identity Physical Change Change without changing identity and no new substances formed

Elements and Symbols Robert Boyle (1627-1691: Elements are substances that cannot be separated into simpler substances Robert had no preconceived ideas about how many elements there might be … Elements are the building blocks of matter gold carbon aluminum Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Number of Elements Matter is composed of 115 different elements (88 naturally occurring)  millions of compounds In comparison, English language has 26 letters  millions of words and sentences Elements not evenly distributed 9 elements in the earth’s crust make up 98% of the mass Oxygen is the most abundant: 20% of air, almost 50% of earth’s crust Elements in living matter also not evenly distributed  selected for biological function Oxygen is still most abundant, followed by carbon, hydrogen, and nitrogen Calcium, phosphorus, magnesium, potassium, sodium, chlorine, sulfur, and iron are all present in significant amounts

Element Names Places of discovery Planets minerals People (Scientists) Element named after many things: Places of discovery Planets minerals People (Scientists) Colors Mythology LecturePLUS Timberlake

Learn the FIRST 20 elements and their names (TEST Material) Symbols of Elements Learn the FIRST 20 elements and their names (TEST Material)

Symbols from Latin Names Some symbols are derived from Latin names as shown below: Cu, copper (cuprum) Au, gold (aurum) Fe, iron (ferrum) Ag, silver (argentum) Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

The Periodic Table: Groups vs. Periods Groups contain elements with similar properties in vertical columns. Periods are horizontal rows of elements. LecturePLUS Timberlake

The Periodic Table

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 Several groups of representative elements have common names Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

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 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Properties of Metals, Nonmetals, and Metalloids Are shiny and ductile Are good conductors of heat and electricity Nonmetals Are dull, brittle, and poor conductors of heat and electricity Are good insulators Metalloids Are better conductors than nonmetals, but not as good as metals Are used as semiconductors and insulators NS: Table 2.5 shows more extensive comparison GR: Table 3.5 LecturePLUS Timberlake

Pause: ALE 2 Group activity: all groups work on problems on ALE IIB worksheet, problems 3-6 Need volunteers to work on the problems written on the board. If no volunteers immediately, will call names. Everyone will do problems on the board sooner or later While working on the problems, ask if you have any questions. I’m more than happy to help LecturePLUS Timberlake

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 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Subatomic Particles Atoms contains subatomic particles. Protons have a positive (+) charge. Electrons have a negative (-) charge. Neutrons are neutral Coulomb's law: Like charges repel and unlike charges attract Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

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 © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Atomic Mass Scale On the atomic mass scale for subatomic particles 1 atom mass unit (amu) is defined as 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, 0.000549 amu LecturePLUS Timberlake

Atomic Number and Mass Number The atomic number Is specific for each element and 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. The mass number : represents the number of particles in the nucleus and is equal to sum of protons and neutrons in the nucleus. Number of protons + Number of neutrons 11 Na Atomic Number Symbol LecturePLUS Timberlake

Atomic Number and Protons 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.

Number of Electrons in Atom Atoms are neutral In each atom, number of protons is equal to that of electrons number of protons = number of electrons For instance, an aluminum atom has 13 protons and 13 electrons. The net charge is zero 13 protons (13+) + 13 electrons (13 -) = 0

Isotopes and Isotopic Notation Elements of same type, same number of protons, but different number of neutrons. Isotopes have identical properties, mass, and sometimes radioactivity Nuclear Symbol Example: Sodium atom

Nuclear Symbols For an atom, the nuclear symbol gives the number of Protons (p+) Neutrons (n) Electrons (e-) 16 31 65 O P Zn 8 15 30 8 p+ 15 p+ 30 p+ 8 n 16 n 35 n 8 e- 15 e- 30 e-

Atomic Mass Na 22.99 Summary The atomic mass of an element Is listed below the symbol of each element on the periodic table. Gives the mass of an “average” atom of each element compared to 12C. Is not the same as the mass number Na 22.99 Summary Atomic mass = average mass of an atom in each element Mass number = # of protons + # of neutrons in the nucleus Atomic number = number of protons in an atom

Learning Check Fill the following table for neutral atoms: Boron 10 Cl Element Name Symbol Atomic Number Mass Number Number of Protons Number of Neutrons Number of Electrons Boron 10 Cl 35 8 16 92 146 6

Elements and Their Atomic Mass Most elements have two or more isotopes that contribute to the atomic mass of that element.

Calculating Average of Masses To calculate an atomic mass, the contribution of each isotope is determined by multiplying the mass of each isotope by its percent abundance and adding the results Example: magnesium has three isotopes, Mg-24 (23.99 amu, 78.70%), Mg-25 (24.99 amu, 10.13%) and Mg-26 (25.98 amu, 11.17%). Calculate the atomic mass of magnesium. Isotope: Mass x Abundance (%) = Contribution to average Mg amu 24Mg 25Mg 26Mg 23.99 24.99 25.98 78.70/100 10.13/100 11.17/100 Average Atomic Mass: 18.88 2.532 2.902 24.31 LecturePLUS Timberlake

Pause: ALE 2 Group activity: all groups work on problems on ALE 2 worksheet, problems 1and 2, 7-9 While working on the problems, ask if you have any questions. I’m more than happy to help LecturePLUS Timberlake

Lecture 2: Atoms and Elements Electron Energy Levels Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Electron Energy Levels Electrons are arranged in specific energy levels that Are labeled n = 1, n = 2, n = 3, and so on. Increase in energy as n increases. Have the electrons with the lowest energy in the first energy level (n=1)closest to the nucleus. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Energy Level Changes An electron absorbs energy to “jump” to a higher energy level. When an electron falls to a lower energy level, energy is emitted. In the visible range, the emitted energy appears as a color. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Energy Emitted LecturePLUS Timberlake Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Sublevels Sublevels Contain electrons with the same energy. Are found within each energy level. Are designated by the letters s, p, d, f. The number of sublevels is equal to the value of the principal quantum number (n). LecturePLUS Timberlake

Number of Sublevels LecturePLUS Timberlake Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Energy of Sublevels In any energy level, The s sublevel has the lowest energy. The s sublevel is followed by the p, d, and f sublevels in order of increasing energy. Higher sublevels are possible, but only s, p, d, and f sublevels are needed to hold the electrons in the atoms known today. LecturePLUS Timberlake

Orbitals An orbital Is a three- dimensional space around a nucleus where an electron is most likely to be found. Has a shape that represents electron density (not a path the electron follows). Can hold up to 2 electrons. Contains two electrons that must spin in opposite directions. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

s Orbitals An s orbital Has a spherical shape around the nucleus. Increases in size around the nucleus as the energy level n value increases. Is a single orbital found in each s sublevel. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

p Orbitals A p orbital Has a two-lobed shape. Is one of three p orbitals that make up each p sublevel. Increases in size as the value of n increases. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Sublevels and Orbitals Each sublevel consists of a specific number of orbitals. An s sublevel contains one s orbital. A p sublevel contains three p orbitals. A d sublevel contains five d orbitals. An f sublevel contains seven f orbitals. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Electrons in Each Sublevel Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Pause: ALE 2 Group activity: all groups work on problems on ALE 2 worksheet, problems 11 and 12 Need volunteers to work on the problems written on the board. If no volunteers immediately, will call names. Everyone will do problems on the board sooner or later While working on the problems, ask if you have any questions. I’m more than happy to help LecturePLUS Timberlake

Lecture 2: Atoms and Elements Electron Configurations Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Order of Filling Energy levels are filled with electrons In order of increasing energy. Beginning with quantum number n = 1. Beginning with s followed by p, d, and f. LecturePLUS Timberlake

Energy Diagram for Sublevels Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Orbital Diagrams An orbital diagram shows Orbitals as boxes in each sublevel. Electrons in orbitals as vertical arrows. Electrons in the same orbital with opposite spins (up and down vertical arrows). Orbital diagram for Li 1s2 2s1 2p filled half-filled empty LecturePLUS Timberlake

Order of Filling Electrons in an atom Fill orbitals in sublevels of the same type with one electron until half full, Then pair up in the orbitals using opposite spins. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Writing Orbital Diagrams The orbital diagram for carbon consists of Two electrons in the 1s orbital. Two electrons in the 2s orbital. One electron each in two of the 2p orbitals Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Individual Learning Check Write the orbital diagrams for A. Nitrogen B. oxygen C. magnesium LecturePLUS Timberlake

Electron Configuration An electron configuration Lists the sublevels filling with electrons in order of increasing energy. Uses superscripts to show the number of electrons in each sublevel. For neon (10 electrons) is as follows: number of electrons sublevel 1s2 2s2 2p6 LecturePLUS Timberlake

Example: Period 1 Configurations In Period 1, the first two electrons enter the 1s orbital LecturePLUS Timberlake

Abbreviated Configurations An abbreviated configuration shows The symbol of the noble gas in brackets that represents completed sublevels. The remaining electrons in order of their sublevels, Example: Chlorine has a configuration of 1s2 2s2 2p6 3s2 3p5 [Ne] The abbreviated configuration for chlorine is [Ne] 3s2 3p5 LecturePLUS Timberlake

Period 2 Configurations Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

TAPPS Learning Check A. The correct electron configuration for nitrogen is 1) 1s2 2p5 2) 1s2 2s2 2p6 3) 1s2 2s2 2p3 B. The correct electron configuration for oxygen is 1) 1s2 2p6 2) 1s2 2s2 2p4 3) 1s2 2s2 2p6 C. The correct electron configuration for calcium is 1) 1s2 2s2 2p6 3s2 3p6 3d2 2) 1s2 2s2 2p6 3s2 3p6 4s2 3) 1s2 2s2 2p6 3s2 3p8 LecturePLUS Timberlake

TAPPS Learning Check A. Cl B. S C. K Write the electron configuration and abbreviated configuration for each of the following elements: A. Cl B. S C. K LecturePLUS Timberlake

Sublevel Blocks on the Periodic Table The periodic table consists of sublevel blocks arranged in order of increasing energy. Groups 1A-2A = s level Groups 3A-8A = p level Groups 3B to 2B = d level Lanthanides/Actinides = f level LecturePLUS Timberlake

Sublevel Blocks LecturePLUS Timberlake Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Writing Electron Configurations Using the periodic table, write the electron configuration for silicon. Solution Silicon is in group 4A, period 3, thus we would stop at 3p and it would have 2 electrons in the 3p orbital: all the sublevel blocks in order gives: 1s2 2s2 2p63s2 3p2 LecturePLUS Timberlake

Electron Configurations d Sublevel The 4s orbital has a lower energy than the 3d orbitals. In potassium K, the last electron enters the 4s orbital instead of the 3d 1s 2s 2p 3s 3p 3d 4s Ar 1s2 2s2 2p6 3s2 3p6 K 1s2 2s2 2p6 3s2 3p6 4s1 Ca 1s2 2s2 2p6 3s2 3p6 4s2 Sc 1s2 2s2 2p6 3s2 3p6 3d1 4s2 Ti 1s2 2s2 2p6 3s2 3p6 3d2 4s2 LecturePLUS Timberlake

Exceptions in Sublevel Block Order Within the filling of the 3d sublevel, exceptions occur for chromium and copper Both Cr and Cu, in the 3d sublevel, are close to either a half-filled or filled sublevel Cr has only 1 electron in the 4s and 5 e-s in the 3d sublevel …half-filled 3d, added stability Cu has 1 e- in 4s and 10 e-s in 3d sublevel … completely filled 3d, stable After 4s and 3d, 4p is filled

Writing Electron Configurations Using the periodic table, write the electron configuration for manganese. Solution 1s2 2s2 2p63s2 3p6 4s2 3d5 LecturePLUS Timberlake

Learning Check A. The last two sublevel blocks in the electron configuration for Co are 1) 3p64s2 2) 4s24d7 3) 4s23d7 B. The last three sublevel blocks in the electron configuration for Sn are 1) 5s25p24d10 2) 5s24d105p2 3) 5s25d105p2 LecturePLUS Timberlake

Learning Check Give the symbol of the element that has A. [Ar]4s2 3d6 B. Four 3p electrons C. Two electrons in the 4d sublevel D. The element that has the electron configuration 1s2 2s2 2p6 3s2 3p6 4s2 3d2 LecturePLUS Timberlake

Pause: ALE 2 Group activity: all groups work on problems on ALE 2 worksheet, problems 12-15 Need volunteers to work on the problems written on the board. If no volunteers immediately, will call names. Everyone will do problems on the board sooner or later While working on the problems, ask if you have any questions. I’m more than happy to help LecturePLUS Timberlake

Lecture 2: Atoms and Elements Periodic Trends Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Valence Electrons The valence electrons Determine the chemical properties of the elements. Are the electrons in the highest energy level. Are related to the Group number of the element. Example: Phosphorus has 5 valence electrons 5 valence electrons P Group 5A(15) 1s2 2s2 2p6 3s2 3p3 LecturePLUS Timberlake

Groups and Valence Electrons All the elements in a group have the same number of valence electrons. Example: Elements in Group 2A(2) have two (2) valence electrons. Be 1s2 2s2 Mg 1s2 2s2 2p6 3s2 Ca [Ar] 4s2 Sr [Kr] 5s2 LecturePLUS Timberlake

Periodic Table and Valence Electrons

Electron-Dot Symbols · Mg · or Mg · or · Mg or · Mg An electron-dot symbol Indicates valence electrons as dots around the symbol of the element. Of Mg shows two valence electrons as single dots on the sides of the symbol Mg. . . · Mg · or Mg · or · Mg or · Mg · Electron-dot symbol Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Writing Electron-Dot Symbols The electron-dot symbols for Groups 1A(1) to 4A(14) use single dots. · · Na · · Mg · · Al · · C · · Groups 5A(15) to 7A(17) use pairs and single dots. · · · · · P · : O · · · LecturePLUS Timberlake

Learning Check State the number of valence electrons for each: A. O 1) 4 2) 6 3) 8 B. Al 1) 13 2) 3 3) 1 C. Cl 1) 2 2) 5 3) 7 LecturePLUS Timberlake

Learning Check State the number of valence electrons for each. A. 1s2 2s2 2p6 3s2 3p1 B. 1s2 2s2 2p6 3s2 C. 1s2 2s2 2p5 LecturePLUS Timberlake

Groups and Electron-Dot Symbols In a group, all the electron-dot symbols have the same number of valence electrons (dots). Example: Atoms of elements in Group 2A(2) each have 2 valence electrons. 2A(2) · Be · · Mg · · Ca · · Sr · · Ba · LecturePLUS Timberlake

Learning Check  A. X is the electron-dot symbol for 1) Na 2) K 3) Al   B.  X   is the electron-dot symbol of 1) B 2) N 3) P LecturePLUS Timberlake

Atomic Size Atomic size is Described using the atomic radius. The distance from the nucleus to the valence electrons. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Atomic Radius Within A Group Increases going down each group of representative elements. Decreases going across each period. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Ionization Energy Ionization energy Is the energy it takes to remove a valence electron. Na(g) + Energy (ionization) Na+(g) + e- LecturePLUS Timberlake

Ionization Energy The ionization energies of Metals are low Nonmetals are high Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings LecturePLUS Timberlake

Pause: Group Work Do all the problems in group activity 2 as group