1. Unit 2 – Electrons and Periodic Behavior
Cartoon courtesy of NearingZero.net

2. Period
The Periodic Table
Group or Family
Group or family
Period

3. Periodic Table Periodic table is divided into 3 classes Metals
Non metals
Metalloids
The horizontal rows are called periods while the vertical columns of the periodic table are called Groups or Families

4. Properties of Metals
Metals are good conductors of heat and electricity
Metals are malleable
Metals are ductile
Metals have high tensile strength
Metals have luster

5. Examples of Metals
Potassium, K reacts with water and must be stored in kerosene
Copper, Cu, is a relatively soft metal, and a very good electrical conductor.
Zinc, Zn, is more stable than potassium
Mercury, Hg, is the only metal that exists as a liquid at room temperature

6. Properties of Nonmetals
Carbon, the graphite in “pencil lead” is a great example of a nonmetallic element.
Nonmetals are poor conductors of heat and
electricity
Nonmetals tend to be brittle
Many nonmetals are gases at room temperature

7. Examples of Nonmetals
Microspheres of phosphorus, P, a reactive nonmetal
Sulfur, S, was once known as “brimstone”
Graphite is not the only pure form of carbon, C. Diamond is also carbon; the color comes from impurities caught within the crystal structure

8. Properties of Metalloids
Metalloids straddle the border between metals and nonmetals on the periodic table.
They have properties of both metals and nonmetals.
Metalloids are more brittle than metals, less brittle than most nonmetallic solids
Metalloids are semiconductors of electricity
Some metalloids possess metallic luster

9. Silicon, Si – A Metalloid
Silicon has metallic luster
Silicon is brittle like a nonmetal
Silicon is a semiconductor of electricity
Other metalloids include:
Boron, B
Germanium, Ge
Arsenic, As
Antimony, Sb
Tellurium, Te

10. The Properties of a Group: the Alkali Metals
  Easily lose valence electron
(Reducing agents)
  React violently with water
  Large hydration energy
  React with halogens to form
salts
(valence electrons are electrons in the outermost shell of an atom)

11. Properties of Alkaline earth metals
They are the group II A elements
Denser, harder and stronger than Group I A elements but less reactive
Too reactive to be found pure in nature

12. Halogens and Noble Gases
Halogens are the most reactive of the non metals.
They are the group VII A elements
The noble gases are the group VIII A elements.
They are also called inert gases because they undergo very few reactions.

13. Periodic Law
When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

14. The Bohr Model of the Atom
I pictured electrons orbiting the nucleus much like planets orbiting the sun.
But I was wrong! They’re more like bees around a hive.
WRONG!!!
Neils Bohr

15. Electron Energy Level (Shell)
Generally symbolized by n, it denotes the probable distance of the electron from the nucleus.
Number of electrons that can fit in a shell:
2n2

16. An orbital is a region within an energy level where there is a probability of finding an electron. This is a probability diagram for the s orbital in the first energy level…
Orbital shapes are defined as the surface that
contains 90% of the total electron probability.

17. Energy Levels, Sublevels, Electrons
Sublevels in
main energy
level
(n sublevels)
Number of
orbitals per
sublevel
Electrons
per sublevel
electrons per
level (2n2) 1 s 2 p 3 6 8 d 5 10 18 4 f 7 14 32

18. Orbital filling table

19. Irregular conformations of Cr and Cu
Chromium steals a 4s electron to half
fill its 3d sublevel
Copper steals a 4s electron to FILL
its 3d sublevel

20. Periodic Trends
How do properties of elements change as you go across a periodic table?

21. Half of the distance between nuclei in
Determination of Atomic Radius:
Half of the distance between nuclei in
covalently bonded diatomic molecule
"covalent atomic radii"
Periodic Trends in Atomic Radius
  Radius decreases across a period
Increased effective nuclear charge due
to decreased shielding
  Radius increases down a group
Addition of principal quantum levels

22. Table of Atomic Radii

23. ION
An atom or a group of atoms that has a positive or negative charge are called ions.
Atoms get a positive charge when they lose electrons
Atoms get a negative charge when they gain electrons
Ionization is the process that results in the formation of an ion.

24. Increases for successive electrons taken from the same atom
Ionization Energy - the energy required to remove an electron from an atom
  Increases for successive electrons taken from
the same atom
  Tends to increase across a period
Electrons in the same quantum level do
not shield as effectively as electrons in
inner levels
    Irregularities at half filled and filled
sublevels due to extra repulsion of
electrons paired in orbitals, making them
easier to remove
  Tends to decrease down a group
Outer electrons are farther from the
nucleus

25. Table of 1st Ionization Energies

26. Electronegativity A measure of the ability of an atom in a chemical
compound to attract electrons
  Electronegativities tend to increase across
a period
  Electronegativities tend to decrease down a
group or remain the same

27. Periodic Table of Electronegativities

28. Summation of Periodic Trends

29. Ionic Radii Cations Anions Positively charged ions formed when
an atom of a metal loses one or
more electrons
Cations
  Smaller than the corresponding
atom
Negatively charged ions formed
when nonmetallic atoms gain one
or more electrons
Anions
Larger than the corresponding
atom