1. Chapter 4

2. Learning Objectives
Understand the development and need for the periodic table
Identify the properties and locations of families on the periodic table
Identify trends of atomic properties

3. Dmitri Mendeleev
1869
63 known
Elements
Arranged by
atomic mass

4. Henry Moseley 1913 Organized elements by atomic
number rather than atomic mass

5. Modern Versions – all follow the periodic law
Theorodore
Benfrey
Timothy
Stowe

6. ADOMAH –
good for electron config.

8. Why do the properties of elements repeat themselves at regular intervals?
Valence Electrons

9. Groups
Periods

10. Main-Group Elements Wide range of properties Solids, liquids, gases
About half are metals
Many are very reactive, some are not reactive
Silicon and oxygen account for four of every five atoms found on or near Earth’s surface

11. Group 1 – Alkali Metals React with water to form alkaline solutions
One valence electron – very reactive
Not found in nature as pure elements
Metals are very soft, easily cut with a knife
Good conductors of electricity

12. Group 2 – Alkaline-Earth Metals
Slightly less reactive than alkali metals
(still very reactive)
Two valence electrons
Harder than alkali metals, higher melting points
Last one in the family,
Radium is radioactive

13. Metals Excellent conductors of electricity Conductors of heat
Some are ductile (can be drawn into a wire)
Some are malleable (can be hammered or rolled into sheets) Mg Sr Hg

14. Transition Metals
Group members do not have identical electron configurations
May lose different numbers of valence electrons during reactions
Less reactive than Group 1&2
Gold, platinum,
and palladium are
the least reactive TMs
Good conductors of heat
Ductile and malleable

15. NonMetals C, N, O, P, S, Se Not good conductors of heat or electricity
Brittle
No metallic luster
Most abundant
elements on earth

16. Metalloids B, Si, Ge, As, Sb, Te, Po
Behave like nonmetals chemically and physically
Electrical conductivity like metals
Semiconductors –
conduct electricity weakly

17. Group 7 - Halogens Most reactive group of non-metals
Seven valence electrons (one short of stable)
F2, Cl2 are gases at RT
Br2 is a liquid at RT
I2 and At2 are solids at RT

18. Group 8 – Noble Gases Also known as noble gases Mostly unreactive
Full set of electrons in outer shell

19. Lanthanides and Actinides
Fill “f” orbitals
Called Lanthanides because they follow Lanthanum on the periodic table
Actinides follow – Actinium
All actinides are radioactive (unstable nuclei)
Shiny metals
Similar in reactivity to
alkaline-earth metals

20. Atomic Radius
How do you measure the radius of an atom?

21. Atomic Radius
One way - Bond Radius

22. Atomic Radius Trends Why? Increasing energy levels
Why? Increasing nuclear charge pulls electrons inward

23. Ionization Energy
The energy required to remove an electron from an atom of an ion

24. Ionization Energy Trends
Father from nucleus
Why? Electron Shielding
Why? Increasing nuclear charge, harder to remove an electron

25. Electron Affinity
The energy change that occurs when a neutral atom gains an electron
Father from nucleus
Why? Electron Shielding
Why? Increasing nuclear charge, goal is to be complete

26. Electronegativity
A measure of the ability of an atom in a compound to attract electrons
Father from nucleus
Why? Electron Shielding
Why? Increasing nuclear charge, stronger (+) attraction

27. Electronegativity
Why is the no color-coding for He, Ne, and Ar?