chapter 4 the periodic table the chemists most valuable tool

Chapter 4The Periodic Table

The

Chemists

Most Valuable Tool

Wanted Poster Project

• Due 11/7/14

• Poster Example

Some Review Terms Element Protons Neutrons Electrons Electron

Configuration

Any substance that cannot be separated by ordinary chemical means

Atomic Number When added to

proton the atomic mass

Neg Charged particle equal to protons in a electro neutral atom

Configuration of electrons in an atomFilled sequentially

What is A Periodic Table? An accepted method of organizing

elements by both repetitive chemical and physical properties

How are elements organized?

Key terms

Periodic Law Valence Electrons

Group Period

History: John Newlands While arranging elements in rows

noticed repeating properties Properties seemed to repeat every eight

elements Law of Octaves

Newlands’ Table

Dmitri Mendeleev Orders all 63 known elements Writes symbols and mass number Orders according to similar properties Able to predict missing elements

properties Luther Myer publishes same periodic

table in the following months

1871 Periodic Table

Why Mendeleev’s Able to predict

properties Predicts properties

to yet undiscovered elements

When elements are discovered Mendeleev’s predictions are correct Gallium,scandium & germanium

Henry Moseley Studies x-ray emissions of protons Notices a correlation Recognizes significance of proton as

atomic number Discovery corrects faults with

Mendeleev’s periodic table

Moseley’s Periodic Table

Latest Change Made by Gene Seaborg While working on the Manhatten Project

identifies a new block of elements Moves the Transuranium elements

(atomic number 58-71 and 90-103) Called the Lanthanide and actinide

Series

Henry Moseley Moseley working

with Rutherford using x-rays discovers a pattern

Discovers Atomic Number

Corrects Mendeleev’s Periodic Table

Modern Periodic Law

Is the principle that certain properties of elements occur periodically when arranged by atomic number.

Why? Valence electrons

Number of electrons in the outer most energy level

Is there More? You BET!!!! Energy levels are the horizontal rows

called a Period. So Germanium (Ar) 3d10 4s2 4p2 Highest energy level is a 4p and a

valence number is 4

Tour the Periodic Table Elements are place in groups (columns) and

periods (rows) Main Group Elements

s-block (1 & 2) and p-block orbitals (13-18) Transition elements

Groups 3-12 d-block Transuranium

f -block

4 Main Blocks

Most elements are metals

Nonmetals

Gases and Liquids

A group of its own Can have both a 1+ and a 1- oxidation

state Either be placed into group 1 or 17

Gas Highly reactive Main component of organic molecules

Group 1Alkali Metals Highly reactive Metals Soft, shiny, Single valence electron Dull quickly when exposed to oxygen Reacts with G-17 to form salts React with water to form alkaline

Introducing Alkaline Earth Metals

Group 2 Alkaline earth metals

& Not as reactive as G-1

G1 vs. G2

Group 17Halogen : means generates salts Valence number of 7 Gain 1 electron to make a complete

outer orbital Form acids in water Astatine one of the rarest natural

occurring element

Introducing The Noble Gas Family

Noble gasesGroup 18 Nearly nonreactive

Formally called inert gases 1962 chemists were able to form

compounds with Xe All elements have a full outer orbital

Metalloids Elements located on the zigzag line Properties of

both metals

and nonmetals

Lanthanide and Actinide f-block elements Lanthanide are shiny metals most similar in

reactivity to alkaline earth metals Actinides are unique in that their nuclei break

apart making them highly radioactive Most of the Elements > 93 are man-made

Other Properties of Metals Wide range of melting & boiling points Metals can be mixed with other metals or

elements to make alloys The mixtures have different properties than

the pure substance Brass Cu & Zn

Harder than Cu and non-corrosive Steel Fe & C small amts of Mn or Ni or Cr

Harder, more flexible, less brittle, lighter, less corrosive Sterling Silver Ag & Cu

Atomic Mass Atomic mass of an element is based on

its relative size compare to Carbon-12 1 atomic mass unit (amu) =

1/12 mass of C-12

Symbols

Atomic NumberName

SymbolAverageAtomicMass

6 Carbon

C 12.01

Crystals and Conduction Bands Crystal- a substance in which atoms or

molecules are arranged in an orderly fashion Electrons in the atoms form bonds that bind

the atoms together Electrons are able to move freely through

conduction unoccupied orbitals forming conduction bands

Crystal Lattice Structure

Polar bondsMolecules or elements

Elements packIn tightest configuration

Exploded View

How do metals conduct electricity? Metals overlap Conduction Bands

Band within which electrons must move to allow electrical conduction

Forbidden Zone Lacking in most metals

Conduction bandOverlapping orbital bands

When bands overlap electrons are able to move freely

Partially filled band

Empty orbital

Semiconductors

Small forbidden zone

Filled band

Empty Conduction band

The forbidden zone (energy gap) is smaller so few electrons are able to enter the conduction band

Nonmetals cannot occupy energy levels in the Forbidden zone (large energy gap).

Filled Band

Empty Conduction Band

Large Forbidden Zone (Energy Gap)

This gap prevents all electrons from reaching the conduction band in an insulator

Thermal conductivity High Electrical conductivity in metals =

high thermal conductivity Due to free movement of electrons and

their very low mass Thermal conductivity is also due to the

ability of a crystal to conduct vibrationsDiamonds are poor electrical conductors but very good conductors of heat due to this