Chapter 3: Elements, Compounds, and the Periodic Table

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Chapter 3 Elements, Compounds,and the Periodic
Table

• Chemistry The Molecular Nature of Matter, 6E
• Jespersen/Brady/Hyslop

2
Discovery of Subatomic Particles

• Late 1800s and early 1900s
• Cathode ray tube experiments showed that atoms
  are made up of subatomic particles
• Discovered negatively charged particles moving
  from the cathode to the anode
• Cathode negative electrode
• Anode positive electrode

3
Discovery of Electron

• JJ Thomson (1897)
• Modified cathode ray tube
• Made quantitative measurements on cathode rays
• Discovered negatively charged particles
• Electrons (e)
• Determined charge to mass ratio (e/m) of these
  particles
• e/m 1.76 x 108 coulombs/gram

4
Millikan Oil Drop Experiment

• Determining charge on Electron
• Calculated charge on electron
• e 1.60 1019 Coulombs
• Combined with Thomsons experiment to get mass of
  electron
• m 9.09 1028 g

5
Discovery of Atomic Nucleus

• Rutherfords Alpha Scattering Experiment
• Most alpha (?) rays passed right through gold
• A few were deflected off at an angle
• 1 in 8000 bounced back towards alpha ray source
• Gave us current model of nuclear atom

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Discovery of Proton

• Discovered in 1918 in Ernest Rutherfords lab
• Detected using Mass Spectrometer
• Hydrogen had mass 1800 times the electron mass
• Masses of other gases whole number multiples of
  mass of hydrogen
• Proton
• Smallest positively charged particle

7
Rutherfords Nuclear Atom

• Demonstrated that nucleus
• has almost all of mass in atom
• has all of positive charge
• is located in very small volume at center of atom
• Very tiny, extremely dense core of atom
• Where protons (p) and neutrons (1n) are located

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Atomic Structure

• Electrons (e)
• Very low mass
• Occupy most of atoms space
• Balance of attractive and repulsive forces
  controls atom size
• Attraction between protons (p) and electrons (e)
  holds electrons around nucleus
• Repulsion between electrons helps them spread out
  over volume of atom
• In neutral atom
• Number of electrons must equal number of protons
• Diameter of atom 10,000 diameter of nucleus

9
Discovery of Neutron

• First postulated by Rutherford and coworkers
• Estimated number of positive charges on nucleus
  based on experimental data
• Nuclear mass based on this number of protons
  always far short of actual mass
• About ½ actual mass
• Therefore, must be another type of particle
• Has mass about same as proton
• Electrically neutral
• Discovered in 1932 by Chadwick

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Properties of Subatomic Particles

• Three kinds of subatomic particles of principal
  interest to chemists

Particle Mass (g) Electrical Charge Symbol
Electron 9.10939 ? 1028 1
Proton 1.67264 ? 1024 1
Neutron 1.67495 ? 1024 0
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Atomic Notation

• Atomic number (Z)
• Number of protons that atom has in nucleus
• Unique to each type of element
• Element is substance whose atoms all contain
  identical number of protons
• Z number of protons
• Isotopes
• Atoms of same element with different masses
• Same number of protons ( )
• Different number of neutrons ( )

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Atomic Notation

• Isotope Mass number (A)
• A (number of protons) (number of neutrons)
• A Z N
• For charge neutrality, number of electrons and
  protons must be equal
• Atomic Symbols
• Summarize information about subatomic particles
• Every isotope defined by two numbers Z and A
• Symbolized by
• Ex. What is the atomic symbol for helium?
• He has 2 e, 2 n and 2 p Z 2, A 4

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Isotopes

• Most elements are mixtures of two or more stable
  isotopes
• Each isotope has slightly different mass
• Chemically, isotopes have virtually identical
  chemical properties
• Relative proportions of different isotopes are
  essentially constant
• Isotopes distinguished by mass number (A)
• e.g.
• Three isotopes of hydrogen (H)
• Four isotopes of iron (Fe)

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Example

• What is the isotopic symbol for Uranium-235?
• Number of protons (p) 92 number of
  electrons in neutral atom
• Number of neutrons (1n) 143
• Atomic number (Z ) 92
• Mass number (A) 92 143 235
• Chemical symbol U
• Summary for uranium-235

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Your Turn!

• An atom of has ___ protons, ___
  neutrons, and ___ electrons.
• 82, 206, 124
• 124, 206, 124
• 124, 124, 124
• 82, 124, 82
• 82, 124, 124

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Learning Check

• Fill in the blanks
• symbol neutrons protons electrons
• 60Co
• 81Br
• 36 29 29

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Carbon-12 Atomic Mass Scale

• Need uniform mass scale for atoms
• Atomic mass units (symbol u)
• Based on carbon
• 1 atom of carbon-12 12 u (exactly)
• 1 u 1/12 mass 1 atom of carbon-12 (exactly)
• Why was 12C selected?
• Common
• Most abundant isotope of carbon
• All atomic masses of all other elements whole
  numbers
• Lightest element, H, has mass 1 u

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Calculating Atomic Mass

• Generally, elements are mixtures of isotopes
• e.g. Hydrogen
• Isotope Mass Abundance
• 1H 1.007825 u 99.985
• 2H 2.0140 u 0.015
• How do we define atomic mass?
• Average of masses of all stable isotopes of given
  element
• How do we calculate average atomic mass?
• Weighted average
• Use isotopic abundances and isotopic masses

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Learning Check

• Naturally occurring magnesium is a mixture of 3
  isotopes 78.99 of the atoms are 24Mg (atomic
  mass, 23.9850 u), 10.00 of 25Mg (atomic mass,
  24.9858 u), and 11.01 of 26Mg (atomic mass,
  25.9826 u). From these data calculate the
  average atomic mass of magnesium.

0.7899 x 23.9850 u 18.946 u 24Mg
0.1000 x 24.9858 u 2.4986 u 25Mg
0.1101 x 25.9826 u 2.8607 u 26Mg
Total mass of average atom 24.3053 u rounds
up to 24.31 u
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Your Turn!

• A naturally occurring element consists of two
  isotopes. The data on the isotopes
• isotope 1 68.5257 u 60.226
• isotope 2 70.9429 u 39.774
• Calculate the average atomic mass of this
  element.
• 70.943 u
• 69.487 u
• 69.526 u
• 69.981 u
• 69.734 u

0.60226 68.5257 u 41.270 u
0.39774 70.9429 u 28.217 u
69.487 u
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Periodic Table

• Summarizes periodic properties of elements
• Early Versions of Periodic Tables
• Arranged by increasing atomic mass
• Mendeleev (Russian) and Meyer (German) in 1869
• Noted repeating (periodic) properties
• Modern Periodic Table
• Arranged by increasing atomic number (Z )
• Rows called periods
• Columns called groups or families
• Identified by numbers
• 1 18 standard international
• 1A 8A longer columns and 1B 8B shorter columns

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Modern Periodic Table
with group labels and chemical families identified
Actinides
Note Placement of elements 58 71 and 90 103
saves space
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Representative/Main Group Elements

• A groupsLonger columns
• Alkali Metals
• 1A first group
• Very reactive
• All are metals except for H
• Tend to form 1 ions
• React with oxygen
• Form compounds that dissolve in water
• Yield strongly caustic or alkaline solution (Na2O)

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Representative/Main Group Elements

• A groupsLonger columns
• Alkaline Earth Metals
• 2A second group
• Reactive
• Tend to form 2 ions
• Oxygen compounds are strongly alkaline (MgO)
• Many are not water soluble

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Representative/Main Group Elements

• A groupsLonger columns
• Halogens
• 7A next to last group on right
• Reactive
• Form diatomic molecules in elemental state
• 2 gases F2, Cl2
• 1 liquid Br2
• 2 solids I2, At2
• Form 1 ions with alkali metalssalts (e.g. NaF,
  NaCl, NaBr, and NaI)

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Representative/Main Group Elements

• A groupsLonger columns
• Noble Gases
• 8A last group on right
• Inertvery unreactive
• Only heavier elements of group react and then
  very limited
• Dont form charged ions
• Monatomic gases (e.g. He, Ne, Ar)

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Transition Elements

• B groupsshorter columns
• All are metals
• In center of table
• Begin in fourth row
• Tend to form ions with several different charges
• e.g.
• Fe2 and Fe3
• Cu and Cu2
• Mn2, Mn3, Mn4, Mn5, Mn6, and Mn7
• Note Last 3 columns all have 8B designation

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Inner Transition Elements

• At bottom of periodic table
• Tend to form 2 and 3 ions
• Lanthanide elements
• Elements 58 71
• Actinide elements
• Elements 90 103
• All actinides are radioactive

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Metals, Nonmetals, or Metalloids

• Elements break down into three broad categories
• Organized by regions of periodic table
• Metals
• Left-hand side
• Sodium, lead, iron, gold
• Nonmetals
• Upper right hand corner
• Oxygen, nitrogen, chlorine
• Metalloids
• Diagonal line between metals and nonmetals
• Boron to astatine

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Metals, Nonmetals, or Metalloids
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Metals

• Most elements in periodic table
• Properties
• Metallic luster
• Shine or reflect light
• Malleable
• Can be hammered or rolled into thin sheets
• Ductile
• Can be drawn into wire
• Hardness
• Some hard iron and chromium
• Some soft sodium, lead, copper

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Properties of Metals

• Conduct heat and electricity
• Solids at room temperature
• Melting points (mp) gt 25 C
• Hg only liquid metal (mp 39 C)
• Tungsten (W) (mp 3400 C)
• Highest mp for a metal
• Chemical reactivity
• Varies greatly
• Au, Pt very unreactive
• Na, K very reactive

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Nonmetals

• Seventeen elements
• Upper right hand corner of periodic table
• Exist mostly as compounds rather than as pure
  elements
• Many are gases
• Monatomic (Noble) He, Ne, Ar, Kr, Xe, Rn
• Diatomic H2, O2, N2, F2, Cl2
• Some are solids I2, Se8, S8, P4, C?
• Three forms of carbon (graphite, coal, diamond)
• One is liquid Br2

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Properties of Nonmetals

• Brittle
• Pulverize when struck
• Insulators
• Non-conductors of electricity and heat
• Chemical reactivity
• Some inert
• Noble gases
• Some reactive
• F2, O2, H2
• React with metals to form ionic compounds

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Metalloids

• Eight Elements
• Located on diagonal line between metals and
  nonmetals
• B, Si, Ge, As, Sb, Te, Po, At
• Properties
• Between metals and nonmetals
• Metallic shine
• Brittle like nonmetal
• Semiconductors
• Conduct electricity
• But not as well as metals
• Silicon (Si) and germanium (Ge)

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Your Turn!

• Which of the following statements is correct?
• Cu is a representative transition element
• Na is an alkaline earth metal
• Al is a metalloid in group 3A
• F is a representative halogen
• None of these are correct

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Your Turn!

• All of the following are characteristics of
  metals except
• Malleable
• Ductile
• Lustrous
• Good conductors of heat
• Acts as a semiconductor

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Ions and Ionic Compounds

• Ions
• Transfer of one or more electrons from one atom
  to another
• Form electrically charged particles
• Ionic compound
• Compound composed of ions
• Formed from metal and nonmetal
• Infinite array of alternating Na and Cl ions
• Formula unit
• Smallest neutral unit of ionic compound
• Smallest whole-number ratio of ions

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Formation of Ionic Compounds

• Metal Non-metal ?? ionic compound
• 2Na(s) Cl2(g) ?? 2NaCl(s)

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Ionic Compounds

• Cations
• Positively charged ions
• Formed from metals
• Atoms lose electrons
• e.g. Na has 11 e and 11 p
• Anions
• Negatively charged ions
• Formed from non-metals
• Atoms gain electrons
• e.g. Cl has 17 e and 17 p

Na has 10 e and 11 p
Cl has 16 e and 17 p
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Experimental Evidence for Ions

• Electrical conductivity requires charge movement
• Ionic compounds
• Do not conduct electricity in solid state
• Do conduct electricity in liquid and aqueous
  states where ions are free to move
• Molecular compounds
• Do not conduct electricity in any state
• Molecules are comprised of uncharged particles

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Ions of Representative Elements

• Can use periodic table to predict ion charges
• When we use North American numbering of groups
  Cation positive charge group number

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Ions of Representative Elements

• Noble gases are especially stable
• Nonmetals
• Negative () charge on anion number of spaces
  you have to move to right to get to noble gas
• Expected charge on O is
• Move two spaces to right
• O2
• What is expected charge on N?
• Move three spaces to right
• N3

N O F Ne
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Rules For Writing Ionic Formulas

• Cation given first in formula
• Subscripts in formula must produce electrically
  neutral formula unit
• Subscripts must be smallest whole numbers
  possible
• Divide by 2 if all subscripts are even
• May have to repeat several times
• Charges on ions not included in finished formula
  unit of substance
• If no subscript, then 1 implied

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Determining Ionic Formulas

• Ex. Formula of ionic compound formed when
  magnesium reacts with oxygen
• Mg is group 2A
• Forms 2 ion or Mg2
• O is group 6A
• Forms 2 ion or O2
• To get electrically neutral particle need
• 11 ratio of Mg2 and O2
• Formula MgO

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Determining Ionic Formulas

• Criss-cross rule
• Make magnitude of charge on one ion into
  subscript for other
• When doing this, make sure that subscripts are
  reduced to lowest whole number.
• Ex. What is the formula of ionic compound formed
  between aluminum and oxygen ions?

Al3 O2
Al2O3
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Your Turn!

• Which of the following is the correct formula for
  the formula unit composed of potassium and oxygen
  ions?
• KO
• KO2
• K2O
• P2O3
• K2O2

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Your Turn!

• Which of the following is the correct formula for
  the formula unit composed of Fe3 and sulfide
  ions?
• FeS
• Fe3S2
• FeS3
• Fe2S3
• Fe4S6

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Cations of Transition Metals

• Transition metals
• Center (shorter) region of periodic table
• Much less reactive than group 1A and 2A
• Still transfer electrons to nonmetals to form
  ionic compounds
• number of electrons transferred less clear
• Form more than one positive ion
• Can form more than one
• compound with same non-metal
• e.g. Fe Cl
• FeCl2 and FeCl3

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Cations of Post-transition Metals

• Post-transition metals
• Nine metals Ga, In, Sn, Tl, Pb, Bi, Uut, Uuq, Uub
• After transition metals and before metalloids
• Two very important ones tin (Sn) and lead (Pb)
• Both have two possible oxidation states
• Both form two compounds with same nonmetal
• e.g. Ionic compounds of tin and oxygen are
• SnO and SnO2
• Bismuth
• Only has 3 charge
• Bi3

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Ions of Some Transition Metals and
Post-transition Metals
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Compounds with Polyatomic Ions

• Binary compounds
• Compounds formed from two different elements
• Polyatomic ions
• Ions composed of two or more atoms linked by
  molecular bonds
• If ions are negative, they have too many
  electrons
• If ions are positive, they have too few electrons
• Formulas for ionic compounds containing
  polyatomic ions
• Follow same rules as ionic compounds
• Polyatomic ions are expressed in parentheses

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Table 3.4 Polyatomic Ions
(Alternate name in parentheses)
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Learning Check

• Ex. What is the formula of the ionic compound
  formed between ammonium and phosphate ions?
• Ammonium NH4
• Phosphate PO43
• Ex. Between strontium ion and nitrate ion?
• Strontium Sr2
• Nitrate NO32

(NH4) (PO4)3
(NH4)3PO4
Sr(NO3)2
Sr2 (NO3)
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Nomenclature (Naming)

• IUPAC system to standardize name of chemical
  compounds
• One system so that anyone can reconstruct formula
  from name
• We will look at naming ionic compounds of
• Representative metals
• Transition metals
• Monatomic ions
• Polyatomic ions
• Hydrates

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Naming Ionic Compounds

• Cations
• Metal that forms only one positive ion
• Cation name English name for metal
• Na sodium
• Ca2 calcium
• Metal that forms more than one positive ion
• Use Stock System
• Cation name English name followed by numerical
  value of charge written as Roman numeral in
  parentheses (no spaces)
• Transition metal
• Cr2 chromium(II) Cr3
  chromium(III)

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Naming Ionic Compounds

• Anions
• Monatomic anions named by adding ide suffix
  to stem name for element
• Polyatomic ions use names in Table 3.5

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Learning Check Name The Following

• K2O
• NH4ClO3
• Mg(C2H3O2)2
• Cr2O3
• ZnBr2

potassium oxide ammonium chlorate magnesium
acetate chromium(III) oxide zinc bromide
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Learning Check Determine The Formula

• Calcium hydroxide
• Ca(OH)2
• Manganese(II) bromide
• MnBr2
• Ammonium phosphate
• (NH4)3PO4
• Mercury(I) nitride
• (Hg2)3N2

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Your Turn!

• Which is the correct name for Cu2S?
• copper sulfide
• copper(II) sulfide
• copper(II) sulfate
• copper(I) sulfide
• copper(I) sulfite

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Your Turn!

• Which is the correct formula for ammonium
  sulfite?
• A. NH4SO3
• B. (NH4)2SO3
• C. (NH4)2SO4
• D. NH4S
• E. (NH4)2S

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Naming Hydrates

• Ionic compounds
• Crystals contain water molecules
• Fixed proportions relative to ionic substance
• Naming
• Name ionic compound
• Give number of water molecules in formula using
  Greek prefixes

mono- 1 hexa- 6
di- 2 hepta- 7
tri- 3 octa- 8
tetra- 4 nona- 9
penta- 5 deca- 10
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Learning Check Naming Hydrates

• CaSO42H2O
• calcium sulfate dihydrate
• CoCl26H2O
• cobalt(II) chloride hexahydrate
• FeI33H2O
• iron(III) iodide trihydrate

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Your Turn!

• What is the correct formula for copper(II)
  sulfate pentahydrate?
• CuSO4 6H2O
• CuSO3 5H2O
• CoSO4 4H2O
• CoSO3 5H2O
• CuSO4 5H2O

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Molecular Compounds

• Molecules
• Electrically neutral particle
• Consists of two or more atoms
• Chemical bonds
• Attractions that hold atoms together in molecules
• Arise from sharing electrons between two atoms
• Group of atoms that make up molecule behave as
  single particle
• Molecular formulas
• Describe composition of molecule
• Specify number of each type of atom present

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Molecules vs. Ionic Compounds

• Molecules
• Discrete unit
• Water two hydrogen atoms bonded to one oxygen
  atom
• Ionic Compounds
• Ions packed as close as
• possible to each other
• Sodium chlorideSix anions surround each
• cation six cations
• surround each anion
• No one ion belongs to another

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Molecular Compounds

• Formed when nonmetals combine
• C O2 ?? CO2 2H2 O2 ?? 2H2O
• Millions of compounds can form from a few
  non-metals
• Organic chemistry and biochemistry
• Deal with chemistry of carbon hydrogen,
  nitrogen, and oxygen
• A few compounds have only two atoms
• Diatomics HCl, CO, HF, NO
• Most molecules are far more complex
• Sucrose (C12H22O11) urea (CON2H4)

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Hydrogen-containing Compounds

• Nonmetal hydrides
• Molecule containing nonmetal hydrogen
• Number of hydrogens that combine with nonmetal
  number of spaces from nonmetal to noble gas in
  periodic table

N O F Ne
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3-D Shapes of Molecules

• Space filling models
• Used to give shapes of simple nonmetal hydrides
• Blue nitrogen
• Red oxygen
• Yellow fluorine
• White hydrogen

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Organic Compounds

• Carbon compounds
• Carbon, hydrogen, oxygen, and nitrogen
• Originally thought these compounds only came from
  living organisms
• Now more general
• Hydrocarbons
• Simplest organic compounds
• Contain only C and H
• All end in ane

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Table 3.8 Hydrocarbons Belonging to the Alkane Series Hydrocarbons Belonging to the Alkane Series Hydrocarbons Belonging to the Alkane Series

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Alkanes

• Boiling point increases as number of carbon atoms
  increases
• Space filling models of alkanes
• Black carbon
• White hydrogen

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Your Turn!

• Which is the correct name for C4H10?
• methane
• ethane
• propane
• D. butane
• pentane

74
Other Hydrocarbons

• Alkenes
• Hydrocarbons with two less Hs than alkanes
• CnH2n
• e.g. C2H4 ethene (ethylene)
• Replace ane ending of alkanes with ene for
  aklenes
• Alkynes
• Hydrocarbons with four fewer Hs than alkanes
• CnH2n 2
• e.g. C2H2 ethyne (acetylene)
• Replace ane ending of alkanes with yne for
  alkynes

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Other Organic Compounds

• Hydrocarbons are basic building
• blocks of organic chemistry
• Many other classes of
• compounds derived from
• them
• Alcohols
• Replace H in alkane with OH group
• e.g. CH3OH methanol (methyl alcohol)
• C2H5OH ethanol (ethyl alcohol)
• Replace e in an alkane name with ol

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Your Turn!

• What is the name of C4H9OH?
• hexanol
• propanol
• pentanol
• tetranol
• butanol

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Writing Formulas for Organic Compounds

• Molecular formula
• Indicates number of each type of atom in molecule
• e.g. C2H6 for ethane or C3H8 for propane
• Order of atoms
• Carbon Hydrogen Other atoms alphabetically
• e.g. sucrose is C12H22O11
• Emphasize alcohol write OH group last
• C2H5OH
• Structural formula
• Indicate how carbon atoms are connected
• Ethane CH3CH3
• Propane CH3CH2CH3

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Your Turn!

• Octane is a hydrocarbon with eight C atoms that
  is the major component of gasoline. What is the
  correct molecular formula for octane?
• C8H14
• C8H16
• C8H18
• C8H17OH
• C8H15OH

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Your Turn!

• What is the correct structural formula for
  octane?
• A. CH3CH2CH2CH2CH2CH2CH2CH3
• B. CH3CH2CH2CH2CH2CH2CH3
• C. C8H18
• D. CH3CH2CH2CH2CH2CH2CH2CH2CH3
• E. CH3CH2CH2CH2CH2CH2CH2CH2OH

80
Nomenclature of Molecular Compounds

• Goal is a name that translates clearly into
  molecular formula
• Naming Binary Molecular Compounds
• Which two elements present?
• How many of each?
• Format
• First element in formula
• Use English name
• Second element
• Use stem and append suffix ide
• Use Greek number prefixes to specify how many
  atoms of each element

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Naming Binary Molecular Compounds

• hydrogen chloride
• phosphorous pentachloride
• triselenium dinitride
• Mono always omitted on first element
• Often omitted on second element unless more than
  one combination of same two elements
• e.g. Carbon monoxide CO
• Carbon dioxide CO2
• When prefix ends in vowel similar to start of
  element name, drop prefix vowel

1 H 1 Cl HCl
1 P 5Cl PCl5
3 Se 2N Se3N2
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Learning Check Name Each

• Format
• Number prefix first element name
• Number prefix stem ide for second element
• AsF3
• HBr
• N2O4
• N2O5
• CO
• CO2

arsenic trifluoride hydrogen bromide dinitrogen
tetroxide dinitrogen pentoxide carbon
monoxide carbon dioxide
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Your Turn!

• Which is the correct formula for nitrogen
  triiodide?
• N3I
• NI3
• NIO3
• N(IO3)3
• none of the above

84
Your Turn!

• Which is the correct name for P4O10?
• phosphorus oxide
• phosphorous decoxide
• tetraphosphorus decoxide
• tetraphosphorus oxide
• decoxygen tetraphosphide

85
Exceptions to Naming Binary Molecules

• Binary compounds of nonmetals hydrogen
• No prefixes to be used
• Get number of hydrogens for each nonmetal from
  periodic table
• Hydrogen sulfide H2S
• Hydrogen telluride H2Te
• Molecules with Common Names
• Some molecules have names that predate IUPAC
  systematic names
• Water H2O ? Sucrose C12H22O11
• Ammonia NH3 ? Phosphine PH3

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Summary of Naming