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

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

3. 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

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

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

6. 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

7. 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

8. 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

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

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

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

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

13. 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!

14. 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

15. 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

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

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

18. Atomic Radius (ATOM SIZE)

19. Atomic Radius (ATOM SIZE)

20. Ne Na

21. 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

22. 9 p+
10 p+ F Ne

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

24. 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

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

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

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

28. 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

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

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

31. Ionization Energy

32. Ionization Energy

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

34. 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

35. Electronegativity

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

37. 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

38. 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.