CH 3 NOTES

Section 3.1

Objectives:

#1 ~ Outline the steps in the historical development of the periodic table

#2 ~ Predict similarities in properties of the elements by using the periodic table.

REVIEW

What are some physical and chemical properties of elements?

What is the relationship of atomic number to the number of protons and electrons?

Repeating Patterns: changes or events that occur in regular, predictable patterns.

DEMO: Activity of Alkali Metals

Purpose: To demonstrate that chemical reactivity follows a predictable pattern related to an element’s position on the periodic table.

Periodicity : the tendency to recur at regular intervals. The properties of the elements repeat in an orderly way from row to row of the table.

History of the Periodic Table

Döbereiner: German chemist who classified elements in groups of three (called triads); the elements in the triad had similar chemical properties, and their physical properties varied in an orderly way according to their atomic mass.

Mendeleev: Russian chemist who organized the elements according to increasing atomic mass; showed repeating patterns of changing properties across horizontal rows; elements in the same column would have similar properties; Mendeleev left blanks where he felt undiscovered elements should go.

The Modern Periodic Table

  • Includes noble gases, transition elements,

lanthanides and actinides…all undiscovered in

Mendeleev’s time.

  • Today’s table organizes the elements based upon increasing atomic number, not atomic mass.

Periodic Law : the physical and chemical properties of the elements repeat in a regular pattern when they are arranged in order of increasing atomic number.

Predicting the Properties of Mystery Elements

MiniLab 1, p. 87

Group 13 / Group 14 / Group 15 / Group 16 / Group 17
Si: 2.4 g/mL
1680 K
118 pm / S: 2.03 g/mL
392 K
103 pm
Ga: 5.89 g/mL
303 K
134 pm / Ge: 5.3 g/mL
894 K
129 pm / As: 5.72 g/mL
1087 K
121 pm / Se: 4.3 g/mL
617 K
120 pm / Br: 3.1 g/mL
266 K
119 pm
Sn: 7.3 g/mL
505K
141 pm / Te: 6.24 g/mL
723 K
138 pm

Answer the Analysis Questions in your notes.

Section 3.2

Objectives:

#1 ~ Relate an element’s valence electron structure by using the periodic table.

#2 ~ Use the periodic table to classify an element as a metal, nonmetal, or metalloid.

#3 ~ Compare the properties of metals, nonmetals, and metalloids.

Group (or Family) : Vertical Column on the Periodic Table

** all elements in the same group have the same number of valence electrons **

Period : Horizontal Row on the Periodic Table

**the period/row number corresponds to the

outermost energy level, so that all elements in

the same period will have the same number of

energy levels

Examples: Li: Group 1, Period 2 (1 v.e- in 2nd E level)

Kr: Group 18, Period 4 (8 v.e- in 4th E Level)

Ra: Group 2, Period 7 (2 v.e- in 7th E Level)

Common Names of Four Groups

  1. Alkali Metals: Group 1
  2. Alkaline Earth Metals: Group 2
  3. Halogens: Group 17
  4. Noble Gases: Group 18 (unreactive or inert)

Classifying Elements

Metals

  • Strong and durable
  • Have luster, conduct heat and electricity
  • Have 1, 2, or 3 v.e- except for Sn, Pb and Bi
  • Bend without breaking (usually)
  • All metals are solid at room temp (200C) exceptfor Hg
  • Groups 3 though 12 are all metals…they are the transition elements (the predictability of valence e- for these metals is NOT very high)
  • Lanthanides : 1st row of inner transition elements or rare earth elements; all have similar properties; atomic number 58 through 71
  • Actinides : 2nd row of inner transition elements; atomic number 90 through 103

Nonmetals

  • Most do not conduct electricity
  • Poorer conductors of heat compared to metals
  • Brittle when solid
  • May exist as a gas at room temp
  • If solid, lackluster
  • Melting points are lower than those of metals
  • Have 5, 6, 7, or 8 valence electrons except carbon (has 4) and helium (2)

Metalloids

  • Some chemical and physical properties of metals and other properties of nonmetals
  • The “stair step” elements; there are 8 : Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te), Polonium (Po), Astatine (At)
  • Some (Si, Ge, As) are good semiconductors

Atomic Structure

Metals

  • Valence electrons are loosely bound to the positive nucleus
  • Electrons are free to move in the solid metal and are easily lost
  • This freedom of motion allows for their good conductivity

Nonmetals/Metalloids

  • Valence electrons are tightly held and are not easily lost
  • Nonmetals and metalloids tend to share their electrons or gain them from other atoms

DEMO: Carbon’s Predictability

Describe the results of this demonstration:

Purpose: To demonstrate that a gas containing carbon can be used as a fuel, but not all carbon-containing gases burn.

Analysis:

  1. What element is combined with carbon in the methane gas?
  2. What element is combined with carbon in the gas generated by reacting baking soda and vinegar?
  3. How do the positions of the elements in questions 1 and 2 relate to the position of carbon on the periodic table?

DEMO: Predicting a Periodic Trend

Definition: Conductivity is the measure of how easily electrons can flow through a material to produce an electrical current.

Purpose: To predict what conductivity trend would be expected in the carbon family (Group 14) and to validate that prediction.

Analysis:

  1. How many valence electrons are present in carbon?
  2. Explain the trend of increasing conductivity down the table in Group 14.

How Do Semiconductors Work?

Electrical Current = the flow of electrons; copper wire is a good example, p.111

Pure silicon is not a good conductor of electricity with its 4 valence electrons…hmmm? What do we do?

Doping : the addition of a small amount of another element to a crystal (like silicon) of a semiconductor.

Phosphorous-doped silicon = n-type semiconductor,

b/c the addition of P results in extra electrons (negative charge).

Boron-doped silicon = p-type semiconductor, b/c the addition of B results in “holes” or positive charges moving throughout the crystal.

APPLY:

If Germanium were used as the basic material for a semiconductor, what elements would be used to dope it?

MATCHING CONCEPTS

Match words or phrases in column 1 with words or phrases in column 2. It is possible to have multiple connections…find as many as you can! BUT, be able to justify the connection!

COLUMN 1COLUMN 2

ConductivityInner Transition Element

GroupFamily

NonmetalState of Matter

MendeleevSemiconductor

Energy LevelMetal

SilverAlkali Metal

LiquidMercury

LanthanidesBromine

SodiumNoble Gas

Alkaline Earth MetalGroup 2

Group 18Periodicity

Halley’s CometGroup 1

SolidMagnesium

MetalloidActinide

7 Energy LevelsGas

1 Valence ElectronPeriod