Unit 4: Periodic Table & Periodic Trends

EQ: How does the organization of the periodic table allow us to make

predictions or determine the behavior & properties of elements?

GPS

• SC4. Students will use the organization of the Periodic Table to predict properties of elements.

• a. Use the Periodic Table to predict periodic trends including atomic radii, ionic radii,

• ionization energy, and electronegativity of various elements.

• b. Compare and contrast trends in the chemical and physical properties of elements and

• their placement on the Periodic Table.

Key Vocabulary Terms

• Law of Octaves• Periodic Table• Periodic Law• Periods• Group/ Family• Valence Electron

• Periodic Trends• Atomic Radius• Ionic Radius• Ionization Energy• Electronegativity• Electron Affinity

The History

• Dobereiner– Found elements could

be put in Triads• Newlands

– Discovered the Octet Rule when classifying elements

• Mendeleev– First to organize

elements by increasing mass to create the Periodic Table

J. W. Dobereiner (1780-1849)

Observed that several elements could be classified into sets of three a.k.a. Triads

His Triads included…. • Lithium, Sodium, and Potassium• Calcium, Strontium, and Barium• Chlorine, Bromine, and Iodine

Triads

• Grouped By Similar Chemical Properties• Many Properties of Middle Elements Are

Approximate Averages Of The Properties Of The 1st And 3rd Element

EXAMPLEELEMENT ATOMIC

MASSDensity

Cl 39.5 1.56

Br 79.9 3.12

L 126.9 4.95

J.A.R. Newlands (1837-1898)

• Presented the idea that when the elements were arranged in order of increasing atomic mass, the properties of every eighth element was like that of the first in the set:1st-8th, 2nd-9th, and so on

• Called the pattern the law of octaves

Dmitri Mendeleev (1834-1907)

Lothar Myer (1830-1895)

• Published nearly identical schemes for classifying the elements

• Mendeleev is given more credit since he published first and was more successful at demonstrating it

• Mendeleev also put breaks in the Table where other elements were yet to be found b/c he knew they had to fit in to make the table work right

Mendeleev

• Noticed that when he arranged the elements by increasing atomic mass he could see a periodic repetition of their properties

• Used this to create the first Periodic Table

• Wanted to make the elements easier to learn and understand

Moseley

• Moseley– Developed atomic

number concept for the atom

– Arranged elements by increasing atomic number rather than mass as Mendeleev had

The Periodic Law

when elements are arranged in order of

increasing atomic number, their physical

and chemical properties show a periodic pattern

A. Periodic Law

• When elements are arranged in order of

increasing atomic #, elements with

similar properties appear at regular

intervals.

0

50

100

150

200

250

0 5 10 15 20Atomic Number

Ato

mic

Ra

diu

s (

pm

)

Reading the Table

• Groups/Families are elements with similar properties and run up and down. There are 18 families.

• Periods run left to right on the table. There are 7 periods.

• Groups to remember– (1)- Alkali Metals – (2)- Alkaline-earth Metals– (3-12)- Transition Metals;

d-block– Inner transition Metals

(bottom); f-block– (17)-Halogens– (18)- Nobel Gases

Reading the Table (Cont.)• Metals

– Have luster (a shine)– Good conductors (of heat &

electricity)– Solids usually– Malleable (can be pounded

into sheets)– Ductile (pulled into a wire)

• Nonmetals– No luster– Poor conductors– Many are Gases– Big variation in

physical properties

Metalloids/ semi-metals

--Have properties of metals and nonmetals-form the steps; except Al.

Electrons and The Table

• Electrons fill atoms in s-, p-, d- and f- orbitals. These orbitals have a location on the P.T.– S-block: left side.– P-block: right side.– D-block: Transition

Metals.– F-block: Inner

Transition Metals.

Classification of the Elements

• The periodic table is divided into blocks that correspond to the sub-levels that are being filled with electrons– S block: Group 1& 2– P block: Groups 13-18

(except for Helium)– D block: transition metals– F block: inner transition

metals

Classification of the Elements

• The periodic table is one of the most important tools in chemistry

• Elements are arranged according to atomic number, but the periodic table also relates to atomic structure and trends among the elements

• Elements can be classified into 4 categories according to their electron configurations

Classification of the Elements

• The noble gases– Elements in which the outermost s and p

sublevels are filled– Also known as inert gases

• The representative elements– Elements in which the outermost s or p sublevel

is only partially filled– Usually called the Group A elements

• Group 1 elements are the alkali metals• Group 2 elements are the alkaline earth metals

Important Group names

• Alkali Metals• Alkaline Earth Metals• Transition Metals• Halogens• Noble Gases

Classification of the Elements

• The transition metals– Metallic elements in which the outermost s

sublevel and nearby d sublevel contain electrons– Called the Group B elements– Characterized by the addition of electrons to the d

orbitals

• The inner transition metals– Metallic elements in which the outermost s

sublevel and the nearby f sublevel generally contain electrons

– Characterized by the filling of f orbitals