Post on 01-Apr-2015
Chapter 6: The Periodic Table
6.1: Development of the Modern Periodic Table
Antoine Lavoisier
• Late 1700’s• 33 elements (known at time) organized in four
categoriesCategory Elements (Old English Names)
Gases Light, heat, dephlogisticated air, phlogisticated gas, inflammable air
Metals Antimony, silver, arsenic, bismuth, cobalt, copper, tin, iron, manganese, mercury, molybdena, nickel, gold, platina, lead, tungsten, zinc
Nonmetals Sulphur, phosphorus, pure charcoal, radical muriatique, radical fluorique, radical boracique
Earths Chalk, magnesia, barote, clay, siliceous earth
Lothar Meyer/Dmitri Mendeleev
• Mid-late 1800’s• Demonstrated a connection between atomic
mass and elemental properties• Arranged elements with similar chemical
properties horizontally• Mendeleev is given more credit because he
published first
Henry Moseley
• Early 1900’s• Realized arranging the elements by atomic mass
was not the best way – some elements ended up in columns with elements of different properties
• Discovered atoms have a unique number of protons (the atomic number)
• Arranged elements in order of increasing atomic number, which resulted in a periodic pattern of properties
Modern Periodic Table
• Groups/Families = vertical columns• Periods = horizontal rows
(Z)
Metalloids – along step line (except for Aluminum)
Properties of Metals
• Conduct heat and electricity• Malleable (can be hammered into thin sheets)• Ductility (can be pulled into wires)• Lustrous (shiny) appearance
• Almost all metals are solids at normal temperatures
Properties of Non-Metals
• Generally lack properties that characterize metals
• Show more variation in properties than metals do
• Many are gaseous at normal temperatures
CLASSIFICATION OF THE ELEMENTSSection 6.2
6.2: Organizing the Elements byElectron Configuration
• Valence electrons– Electrons in the outermost principal energy level– Number of valence electrons correspond to the
representative elements group number (Group 1 has 1 valence electron, Group 2 has 2 valence electrons, Group 13 has 3 because it is the 3rd representative group, etc)
– Energy level of valence electrons correspond to the period number (Period 4 valence electrons are in the 4th energy level and so on…)
The s-, p-, d-, and f-Block Elements
• We saw these with our little “cheat sheets”• This shows which sublevel is being filled
PERIODIC TRENDSSection 6.3
PERIODIC TREND QUIZ
1)What group is the:– Noble Gases– Alkali Metals– Halogens– Transition Metals2)Identify the # of valence electrons for each
group/family.3)An element with an acquired (+) or (-) charge is
termed an _____.
QUIZ CONT.
4)Identify what groups represent:– S block = – P block = – D block = – F block = 5) Why do elements “give up” or “take” electrons?
Think in terms of outer shell, what is this outer shell called?
What are Periodic Trends?
• Many properties of the elements change in a predictable way, based on their location in the periodic table
• We will look at the following properties:– Atomic radius– Ionic radius– Ionization energy – the energy req’d to remove an
electron from a gaseous atom– Electronegativity – ability of an atom to attract
electrons in a chemical bond
Atomic Radius
• Trends within periods– Decrease in atomic radius as you move from left
to right across a period
• Trends within groups– General increase in atomic radius as you move
down a group
Ionic Radius
An ION is an atom or bonded group of atoms that has a positive or negative charge
• When atoms lose electrons and become positive ions, they always become smaller
• When atoms gain electrons and become negative ions, they become larger
Ionic Radius (cont’d)
• Trends within periods (see Fig 6.14)– Generally, as you move from left to right across a
period, the size of the positive ions decrease– Then, beginning in group 15 or 16, the size of the
much-larger negative ions also gradually decreases
• Trends within groups– As you move down a group, ionic size gradually
increases
Ionization Energy
• Trends within periods– Values of first ionization energies generally
increase as you move from left to right across a period.
• Trends within groups– First ionization energies generally decrease as you
move down a group
The Octet Rule
• Atoms tend to gain, lose, or share electrons in order to acquire a full set of eight valence electrons
• Exception: Hydrogen does not want 8 valence electrons it will usually give up it’s one electron to make a positive ion
Electronegativity
• Electronegativity values range from 0.7 to 3.98
• Fluorine is the most electronegative atom (3.98)• Francium is the least electronegative atom (0.70)
• Many periodic tables list electronegativity values as well