Warm Up: Why do you think elements in the same GROUP have similar properties? Today: Organizing a Periodic Table Homework: None

Mendeleev ( 1860 ) – Developed Periodic Table based on atomic weight, noticed that when arranged this way they exhibit apparent periodicity of properties

The Evolution of the Periodic Table The modern Periodic Table is arranged by atomic number rather than weight, and Henry Moseley (1914) is given credit for this. Groups Periods

Periodicity The repetition of chemical properties Demonstrate themselves as patterns in the Periodic Table

The Periodic Table more reactive (more metallic) (more nonmetallic) METALS METALLOIDS NONMETALS

Metals, Nonmetals and Metalloids Tend to LOSE electrons to form positive ions (cations) Nonmetals: Tend to GAIN electrons to form negative ions (anions) Metalloids: Have mixtures of metallic and nonmetallic properties

The Octet Rule Oct = 8 Elements are the most stable when they have 8 valence electrons Octet Rule: Atoms will gain, lose, or share electrons to make a total of 8 valence electrons +1 -1 Li F

INNER TRANSITION METALS The Periodic Table Cu Ag Au NOBLE GASES MAIN BLOCK ALKALI ALKALINE EARTH HALOGENS TRANSITION METALS INNER TRANSITION METALS inert more reactive

Which element is a transition metal? tin copper tellurium cesium E) neon

Which of the following selections contains only main block elements? Cu, Co, Cd Hg, Cr, Ag Al, Mg, Li D) Ni, Fe, Zn

Which is more reactive? Na or Rb? Na or Cu? F or Br?

Valence Electrons 1s22s22p63s1 1 valence electron! 1s22s22p63s23p64s1 For sodium: For potassium: 1s22s22p63s1 1 valence electron! 1s22s22p63s23p64s1 1 valence electron!

Valence Electrons 1s2 2s2 2p6 3s2 3p5 7 valence electrons! For chlorine: For bromine: 1s2 2s2 2p6 3s2 3p5 7 valence electrons! 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 7 valence electrons!

Valence Electrons 1 2 3 4 5 6 7 8 The pattern? For the main block elements (s and p blocks), the number of valence electrons matches the column number 1 2 3 4 5 6 7 8

INNER TRANSITION METALS +1 +2 +3 -3 -2 -1 MAIN BLOCK TRANSITION METALS -4 INNER TRANSITION METALS 1 2 3 4 5 6 7 8 +4

How many valence electrons are in an atom of… chlorine potassium helium

What is the oxidation number for the ion of… calcium arsenic lithium

Atomic Radius (ATOM SIZE)

Atomic Radius (ATOM SIZE) http://encarta.msn.com

Ne Na

Each period number in the periodic table corresponds to _______ A) atomic mass B) a principal energy level C) an energy sublevel D) an atomic number

9 p+ 10 p+ F Ne

Effective Nuclear Pull Periodic Trends Shielding Effect (energy levels) Nuclear Pull (protons) Effective Nuclear Pull

How does atomic radius (the size of the atom) change from left to right across a period in the periodic table? A) It first decreases, then increases B) It first increases, then decreases C) It tends to increase D) It tends to decrease E) It does not change

Which of the following elements has the smallest atomic radius? sulfur selenium chlorine bromine

CATION SIZES “Parent” atom Cation Loss of energy level Na Na

ANION SIZES “Parent” atom Anion more electrons = more repulsion F F

Why is the radius of a negative ion always greater than the radius of its neutral atom? A) because atomic orbitals contract all by themselves B) because the number of principal energy levels is always reduced C) because electron speeds are reduced D) because repulsion between electrons increases when electrons are gained

Which atom is bigger? Na or P O or Se Mg or Mg+2 Br or Br-1 K+1 or Cl-1

The Periodic Table Ionization Energy The amount of energy required to remove the outermost electron from an atom Energy

Ionization Energy

Ionization Energy

Which of the following elements has the smallest ionization energy? potassium sodium magnesium D) calcium

The Periodic Table Electronegativity The attraction an atom has for an electron in a bond Elements that do not make bonds (the noble gases) do not have electronegativities. Determined on the Pauling Scale (0 – 4) Shielding effect decreases electronegativity http://nanotech.sc.mahidol.ac.th/genchem/bonding1/en.jpg http://web.visionlearning.com

Electronegativity

Which group of the periodic table has the highest electronegativity? the alkalki metals the alkaline earth metals C) the noble gases D) the halogens

Across period (left to right) Down group (top to bottom) Recap Fill in the trends below with “increasing” or “decreasing” and a brief explanation for why. Across period (left to right) Down group (top to bottom) Atomic Radius Ionic Radius Ionization energy Electronegativity

Check Your Understanding Which element is bigger? N or As N or F Which ion is bigger? The ion of Mg or the ion of Cl? The ion of Mg or the ion of F? Order the elements from lowest to highest electronegativity: Li, Rb, Na, O, He Explain why the first ionization energy for potassium is less than for sodium.