X Unit 11: The Periodic Table

History of the Periodic TableHistory of the Periodic Table

Antoine Lavoisier (1743 – 1794)– Published Elements of Chemistry in

1789•Included a list of “simple

substances” (which we now know to be elements)

•Formed the basis for the modern list of elements

– Only classified substances as metals or nonmetals

History of the Periodic TableHistory of the Periodic Table

Johann Döbereiner (1780 – 1849)– Classified elements into “triads”

•Groups of three elements with related properties and weights

• Began in 1817 when he realized Sr was halfway between the weights of Ca and Ba and they all possessed similar traits

– Döbereiner’s triads:• Cl, Br, I S, Se, Te• Ca, Sr, Ba Li, Na, K

History of the Periodic TableHistory of the Periodic Table

John Newlands (1837 – 1898)– Law of Octaves (1863)

• Stated that elements repeated their chemical properties every eighth element

• Similar to the idea of octaves in music

History of the Periodic TableHistory of the Periodic TableDmitri Mendeleev (1834 – 1907)

– Russian chemist (“The father of the P.T.”)

– Arranged elements based on accepted atomic masses and properties that he observed

– Listed elements with similar characteristics in the same family/group•Left blank spots for predicted

elements which would be discovered later

Dmitri Mendeleev (1834 – 1907)

Dmitri Mendeleev (1834 – 1907)

Property Mendeleev’s Prediction for

“eka-silicon” in 1871

Observed Properties of Germanium

(discovered in 1886)

Atomic Weight

72 72.59

Density (g/cm3)

5.5 5.35

Melting Point (°C)

High 947

Color Dark gray Grayish white

Formula of oxide

XO2 GeO2

History of the Periodic TableHistory of the Periodic TableHenry Moseley (1887 – 1915)

– English physicist– Arranged elements based on increasing

atomic number•Remember: atomic number = # of p+ in

nucleus

– Periodic table looked similar to Mendeleev’s design since as atomic number increases, so does the atomic mass

Periodic LawPeriodic Law

• Periodic – occurring at regular intervals– Relates to trends on the periodic table

of elements

• Modern Periodic Law– When elements are arranged in order

of increasing atomic number, there is a periodic repetition of their properties

Reading the Periodic TableReading the Periodic Table

• Periods– “Horizontal Rows” on the periodic

table

• Groups (or Families)– “Vertical Columns” on the periodic

table

Reading the Periodic TableReading the Periodic Table

•Metalloids – elements having properties of both metals and nonmetals

Properties of Metals/Non-metals/Metalloids

• Metals - shiny, smooth, solid at room temperature, good conductors of heat and electricity, malleable and ductile.

• Metalloids (along stair step line) physical and chemical properties of both metals and nonmetals- B, Si, Ge, As, Sb, Te

• Nonmetals – low melting and boiling points, brittle, dull-looking solids, poor conductors of heat and electricity.

Reading the Periodic TableReading the Periodic Table• Valence e- are periodic!• Notice the similarities

– Ex.) Write the noble gas configurations for:•F

•Cl

•Br

•I

– GROUPS have similar valence electron configurations!

Groups of ElementsGroups of Elements

• Group 1 = Alkali Metals– Located in Group 1 (except Hydrogen)– Extremely reactive

• Want to lose 1 e- to become “noble gas-like”

• Group 2 = Alkaline Earth Metals– Also very reactive– Both Group 1 & 2 occur naturally as

compounds not elements

Cutting sodium metalCutting sodium metal

Reaction of potassium + H2O

https://www.youtube.com/watch?v=oqMN3y8k9So https://www.youtube.com/watch?v=Jy1DC6Euqj4

Group 1: Alkali MetalsLi, Na, K, Rb, Cs

MagnesiumMagnesium

Magnesium Magnesium oxideoxide

Group 2: Alkaline Earth MetalsGroup 2: Alkaline Earth MetalsBe, Mg, Ca, Sr, Ba, RaBe, Mg, Ca, Sr, Ba, Ra

https://www.youtube.com/watch?v=qSr39UwpELo

Groups of ElementsGroups of Elements

• Group 17 = Halogens– Very active nonmetals

•Want to gain 1 e- to become like a noble gas

Groups of ElementsGroups of Elements• Group 18 = Noble Gases

– Sometimes called “inert gases” since they generally don’t react•Mainly true, but not always (Kr, Xe will

react sometimes)•Have a full valence shell (8 e-)

Groups of ElementsGroups of Elements• Transition Metals

– Located in the center of the Periodic Table– 10 elements wide (“d” orbitals)– Semi-reactive, valuable, crucial to many

life processes

• Lanthanides and Actinides– Located at the bottom of the Periodic Table– 14 elements wide (“f” orbitals)– Some are radioactive, though not all– Lanthanides = Period 6– Actinides = Period 7

Alkali Metals =

Alkaline Earth Metals =

Transition metals =

Metalloids = Lanthanides =

Halogens = Actinides =

Noble Gases =

Periodic Properties & TrendsPeriodic Properties & Trends

• Electronegativity– Ability of an atom to pull e- towards itself– Linus Pauling: developed scale to

demonstrate different electronegativity strengths

– Increases going up and to the right• Across a period more protons in nucleus

= more positive charge to pull electrons closer• Down a group more electrons to hold onto

= element can’t pull e- as closely

• Electronegativity– Ability of an atom to pull e- towards itself– Across a period more protons in nucleus

= more positive charge to pull electrons closer– Down a group more electrons to hold onto

= element can’t pull e- as closely

Periodic Properties & TrendsPeriodic Properties & Trends

Periodic Properties & TrendsPeriodic Properties & Trends• Atomic Radius

– Distance between the nucleus and the furthest electron in the valence shell

– Increases going down and to the left•Down a group more e- = larger radius•Across a period elements on the right

can pull e- closer to the nucleus (more electronegative) = smaller radius

• *Remember*– LLLL Lower, Left, Large, Loose

Periodic Properties & TrendsPeriodic Properties & Trends• Atomic Radius

– Increases going down and to the left

• *Remember*LLLL Lower, Left, Large, Loose

Memory DeviceMemory Device

LLLL: Lower Left, Larger AtomsLLLL: Lower Left, Larger Atoms

Periodic Properties & TrendsPeriodic Properties & Trends

• Ionization Energy– Energy required to remove an e- from the

ground state

– 1st I.E. = removing 1 e-, easiest– 2nd I.E. = removing 2 e-, more difficult– 3rd I.E. = removing 3 e-, even more difficult

• Ex.) B --> B+ + e- I.E. = 801 kJ/mol• Ex.) B+ --> B+2 + e- I.E.2 = 2427 kJ/mol • Ex.) B+2 --> B+3 + e- I.E.3 = 3660 kJ/mol

Periodic Properties & TrendsPeriodic Properties & Trends

Ionization Energy• Increases going up and to the right

– Down a group more e- for the nucleus to keep track of = easier to rip an e- off

– Across a period elements on the right can hold electrons closer (more electronegative) = harder to rip an e- off

Periodic Properties & TrendsPeriodic Properties & Trends• Metallic Character

– How “metal-like” an element is•Metals lose e-

– Most Metallic: Cs, Fr– Least: F, O

– Increases going down and to the left

Think about where the metals & nonmetals are located on the periodic table to help you

remember!

Periodic Properties & TrendsPeriodic Properties & Trends• Ionic Radius

– Radius of an atom when e- are lost or gained different from atomic radius

– Ionic Radius of Cations• Decreases when e- are removed

– Ionic Radius of Anions• Increases when e- are added

Sizes of IonsSizes of Ions

• CATIONS are SMALLER than the atoms from which they are formed.

• Size decreases due to increasing he electron/proton attraction.

Li,152 pm3e and 3p

Li+, 78 pm2e and 3 p

+

Sizes of IonsSizes of Ions

• ANIONS are LARGER than the atoms from which they are formed.

• Size increases due to more electrons in shell.

F, 71 pm9e and 9p

F-, 133 pm10 e and 9 p

-

Overall Periodic Trends

Property Group Trend Period Trend

Atomic RadiusIncreases going

downIncreases to the

left

Ionization EnergyIncreases going

upIncreases to the

right

ElectronegativityIncreases going

upIncreases to the

right

Metallic CharacterIncreases going

downIncreases to the

left

Summary of Periodic Trends