Chapter 8 Periodic Table of Properties

Review: Mendeleev’s Periodic Table

Periodic Law

• Recall from C7…Elements in the same group (vertical column) have the same number of valence electrons resulting in similar properties

• This idea can be used to predict physical properties of elements and called Periodic Trends!

Periodic Trends: Atomic Radius (size)

Trend in Atomic Radius Explained:

• Why does atomic radius decrease across a period?– Higher # = more protons = higher core charge

• Increased attraction between p+ & e-– e- pulled closer to nucleus = ????

• Why does atomic radius increase down a group?– Valence electron shell higher n = higher probability of

finding e- further from nucleus = ????– Shielding by core e- = less pull on valence e- = ????

Periodic Trends in Ionic (-) Radius

Periodic Trends in Ionic (+) Radius

Trend in Ion Size Explained:

• Cation (+) radii are smaller than atomic radii– Why?• Lose of valence e- • Results in lower n, resulting in stronger nuclear pull

• Anion (-) radii are larger than atomic radii– Why?• Gain of e-• Results in increased repulsion between e-

Can you explain the following?

Properties of Metals

¾ of all known elements• Solid at room temp (NOT Mercury)• Low IE = give up electrons• Metallic bonds– Delocalization• Malleable, ductile

Alkali Metals

• Alkali Metals Video• React with not only water, but many other

substances– Do not find in elemental state

• Sodium and potassium– Relatively abundant– nerve impulses• Your body would not function correctly w/out these• Ion imbalance effects

Alkaline earth metals

• Alkali and Alkaline Earth Metals Video• Denser, harder, higher melting & boiling• Less reactive– Still not found in elemental form

• Magnesium and calcium most abundant– Magnesium is the most important

• Alloys

– Calcium most commonly CaCO3

• Seashells, limestone

– Hard Water

Aluminum

• Earth’s crust• Commercial production• Aluminum Video

Transition Elements

• Reactivity• In nature• Hardness & melting/boiling points• Color• Magnetism• LAB: Colorful Transition Metals

Uses of Transition Metals

• Copper– Coins – nickel and penny– *Electrical conductor – Water transport

• Silver– Photographic film

• Alloys– Different properties (chemical and physical) than individual

metals• Increased strength, hardness• Lower electrical and thermal conductivity• Lower melting point

Properties of Alloys (Cont)

Impurities (in this case, C) occupy the spaces between atoms

This makes the alloy stronger because atoms cannot slide past each other

Lower electrical conductivities result because impurities block the path of e- in the electron sea

Lower melting points result due to imperfect crystalline structure

Fe

C

Metalloids

• Properties of both metals and nonmetals– Nonmetallic structure and chemical behavior– Luster– Conduct electricity• Not as well as metals = semiconductors

• Silicon– Metallic luster, but diamond structure– Most common metalloid– Quartz

Metalloids as Semiconductors

• Remember: Silicon is poor conductor– Certain impurities increase conductivity• As small as 1 : 1,000,000!!• Called doped crystals

– Impurities affect silicon in two ways• N-type • P-type

– Junctions: n-type next to p-type

Nonmetals - Carbon

• Distribution• Allotropes

Nonmetals – Nitrogen Family

• Natural occurrence• Reactivity• Nitrogen cycle

N2 + 8H+ + 8e- + 16 ATP  2NH3 + H2 + 16ADP + 16 Pi

2 NO3− + 10 e− + 12 H+ → N2 + 6 H2O

Nitrogen Family (cont)

• Phosphorus– White phosphorus• Reactivity• Physical properties• toxicity

– Red phosphorus• Physical properties

Nonmetals – Oxygen Family

• Oxygen– Abundance– Reactivity– Cellular respiration– O3 allotrope

• Sulfur– Abundance– Industrial

iron and steel (cars, appli-ances); 1%

other industrial (explsoives,

synthetic rub-ber); 6%

Petroleum (aviation, gaso-

line, lubricants); 2%

Pigments, fibers and film;

3%

Mixed fertilizers; 54%

Titanium and pigments (paints,

linoleum, paper); 5%

Chemicals (detergents, food additives, catalysts, an-

tifreeze); 17%

Nonmetals – Halogens and Noble Gases

• Diatomic• Reactivity– Halogens Video

Nonmetals - Noble Gases

• Helium• Neon• Argon• Krypton• Xenon• Radon