1. CHAPTER 6: Periodic Table

2. Development of Periodic Table
Mendeleev
Contributions – made very first periodic table
p.t. arrangement: elements ordered by increasing atomic mass

3. Development of Periodic Table
3) Noticed periodic pattern (repetition) in element properties
- elements placed in groups w/ similar properties
- Left gaps for substances yet to be discovered

4. Mendeleev’s Periodic Table (1871)

5. 4) errors: when new elements discovered, several elements on his table didn’t fit right
- had different properties

6. Moseley
periodic table arrangement: elements ordered by increasing atomic number
Periodic Law – when elements arranged by increasing atomic number, their physical & chemical properties show a periodic pattern

7. Modern Periodic Table Boxes contain: Element name Element symbol
Atomic number
Atomic mass

8. Modern Periodic Table Arrangement – increasing atomic number
a) groups – columns (vertical)
b) periods – rows (horizontal)

9. Two Divisions of Elements
Main Group Elements – groups 1A, 2A and 13-18A
(s & p block)

10. Two Division Of Elements
Transition Elements – group 3-12B elements (d block)

11. Classifying Elements Metals – elements w/ shine – solid @ room temp
– conducts heat & electricity
– malleable: put into thin wires
– ductile: pound into sheets

12. Metals a) Alkali Metals – group 1A (except H)
- highly reactive, very soft
b) Alkaline Earth Metals – group 2A
- less reactive and denser than alkali metals
c) Transition Metals – d-block (group 3-12B)

13. Metals La Ac d) Inner transition metals – f-block
i) Lanthanide Series – row 1 of f-block
ii) Actinide Series – row 2 of f-block La Ac

14. Nonmetals Defn - gases or brittle, dull looking solids
- poor conductors of heat & electricity
a) Halogens
b) Noble Gases
- group 17A
- highly reactive
- group 18A
- very unreactive/stable

15. Metalloids Defn – BORDER THE STAIRSTEP LINE 
- Have similar chem & phys props as both metals
and nonmetals

16. Alkali metals
Alkaline earth metals
Halogens
Noble Gases
Transition Metals
Lanthanides
Actinides

17. Organizing Elements By Electron Configuration
Valence Electron – electrons in highest energy level
atoms in same group have similar chemical
props b/c they have same # of valence e-

18. Valence Electrons And Period
The period indicates what energy level the valence electrons are located on
Ex: [Ar] 4s2 3d10 4p1
3 Valence e-
on 4th energy
level

19. Valence Electrons and Group Number
# of valence electrons equals group number (only for main group elements)
exception: Helium
(in group 18, but has
2 valence e- only)

20. Ex Problems [Ne] 3s2 [He] 2s2 2p4 [Kr] 5s2 4d105p5 2 16 17 3 2 5 s p p
Tell the group, period, and block where these elements are located
[Ne] 3s2
[He] 2s2 2p4
[Kr] 5s2 4d105p5 2
group –
period –
block –
group –
period –
block – 16
group –
period –
block – 17 3 2 5 s p p

21. Periodic Trends
There are certain patterns that occur with the elements as you go across and down the periodic table
which atom is the biggest? smallest?
which atom is most reactive/least stable?

22. Atomic Radius (size)
Defn – distance from center to edge of electron cloud
Period Trend – decreases from left to right
Why?
increasing # of protons (+ charge) in nucleus has a greater attraction for
electrons (- charge)

23. Atomic Radius Group Trend – increases from top to bottom Why?
electrons occupy higher energy levels and are farther from the nucleus
Period 1
Period 2
Period 3

24. Atomic Radius
Summary
decreases
increases

25. Ion Defn – atom w/ a positive or negative charge
- atom lost or gained electrons
- # protons ≠ # electrons

26. Cation Defn – positive ion (atom lost e-)
- more protons than electrons
Comparing atom size vs. its cation size A A+
atom A
cation of atom A
cations are SMALLER than its original atom

27. Anion Defn – negative ion (atom gained e-)
- more electrons than protons
Comparing atom size vs. its anion size A- A
atom A
anion of atom A
anions are LARGER than its original atom

28. Ion Summary A- A A+
<
<
cation
atom
anion

29. Ionization Energy
Defn – energy required to remove an electron from an atom
Period trend – IE increases from left to right
Why?
increased nucleus charge has greater hold on valence e-

30. Ionization Energy Group Trend – IE decreases from top to bottom Why?
atomic size increases, valence e- are farther away so easier to remove (less energy required)

31. Period 1
Period 2
Period 3

32. Ionization Energy
Summary
increases
decreases

33. Ex problem Cl > Ba > Cs
Rank these atoms from increasing to decreasing ionization energy: Ba, Cs, Cl
increases
decreases Cl Cs Ba
Cl > Ba > Cs

34. Electronegativity
Defn – relative ability of an atom to attract electrons in a chemical bond
“how badly does atom want electrons” while in a bond
Period Trend – increases from left to right
Group Trend – decreases from top to bottom

35. Electronegativity
Summary
increases
decreases

36. Ex problem O > Mg > Sr
Rank these atoms from high to low electronegativity: O, Sr, Mg
increases
decreases Mg O Sr
O > Mg > Sr