Environmental Chemistry Unit 2 Materials:

Structure and Uses

http://www.ccsdualsnap.com/miscellan.htm

Coin Design Competition

• How are coins made?

• http://www.usmint.gov/mint_tours/index.cfm?action=vtShell

Link to Previous Learning

• We have learned about physical properties of matter: – Physical properties: Property of an object that can be

observed or measured without changing the substance

• We have also learned the names and symbols of common elements

• In this unit we will learn about chemical properties, organization of the elements on the periodic table and how it relates to properties of the atom

Properties Make the Difference

Section 1

Coin-Design Competition

• In order to apply for the Coin-Design Competition, we must decide the composition of the coins material

• Need to research the properties of elements that could be used to make the coin

Physical and Chemical Properties of Elements

Physical Properties• Property of an object that

can be observed or measured ______________

________________________

• Examples: – Density– Color– Melting Point

Chemical Properties• _______________________

_______________________• Must alter substance to

observe• Indicates how a substance

_______with something else

• Examples:– Flammability

Physical and ChemicalChanges

Physical Changes• ____________________

of the substance

• Examples: – Crush– tear – change in state (solid-

liquid-gas)

Chemical Changes• ________________

________________

• Examples: – food cooks– iron rusts– wood burns

Study Buddy ReviewClassify each as a physical or chemical

property of matter:

• Blue Color• Ability to Rust• Density• Flammability• Reacts with a base to form water• Boiling Point• Reacts with water to form a gas• Luster• Mass• Odor

The Periodic Table of Elements

(Section 4)

Chemical Elements

• Elements: Pure substances that __________

_____________________________________– Composed of atoms– Organized by the Periodic Table of Elements

Dobereiner’s TriadsTHE LAW OF TRIADS:The atomic mass of the middle element of the triadis equal to the ________________________ of theother two elements.

EXAMPLE: Lithium Atomic Mass of 7Sodium Atomic Mass of 23Potassium Atomic Mass of 39

According to Dobereiner’s Law, the atomic mass of sodium Should equal the arithmetic mean of lithium and potassium.(7+39)/2 = 23, which is the mass of sodium.

Problems with Dobereiner’s Law of Triads.

1) ______________________________________________________________________________________________

2) The law did not work for very low or very highmassed elements such as F, Cl, and Br.

3) As techniques improved for measuring atomicmasses accurately, the law became obsolete.

Dobereiner’s research made chemists look at groups ofelements with similar chemical and physical properties.

Newland’s Law of Octaves

When placed in increasing order of their atomicmasses, every __________________________and _________________________.

Li Be B C N O FNa Mg Al Si P S ClK Ca

Problems with Newland’s Law of Octaves

1) It was not valid for elements that had atomicmasses higher than Ca.

2) When more elements were discovered(Noble gases) they could not be accommodated in histable.

However, the modern periodic table does draw from theconcept of periods of eight.

Mendeleev and Meyer

• Published nearly identical schemes for classifying elements

• Arranged elements by ______________________• Mendeleev generally given more credit

– Published first– More successful at demonstrating value of table– Predicted discovery of new elements, properties

of new elements

Mendeleev’s Table: the first periodic table of the elements.He arranged the table so that elements in the __________________________________________________.

Problems with Mendeleev’s Table:

1) The positions of isotopes could not beaccommodated within the table.

2) In order to make the elements fit the requirements,Mendeleev was forced to put an element of slightlyhigher atomic weight ahead of one of slightly lower atomic weight.

Henry Moseley (1887-1915)

• Developed concept of ________________

– amount of positive charge in the nucleus

• Later determined that arranging periodic table according to increasing atomic number eliminated problems seen in Mendeleev’s table

Why is it the “periodic” table?

• Periodic Law: when elements are arranged in order of __________

_________________, their physical and chemical properties show a periodic pattern

Study Buddy Review

• Describe the contribution each person below made to the development of the periodic table:– Johan Dobereiner– John Newland– Dmitri Mendeleev– Julius Meyer– Henry Moseley

Parts of the Periodic Table

Parts of Periodic Table

• Groups/families: vertical columns– Alkali metals: – Alkali earth metals: – Boron, carbon, nitrogen, oxygen families– Halogens: – Noble gasses:

• Horizontal rows are called ___________

• There are 7 periods

1A

2A 3A 4A 5A 6A7A

8A0

• The elements in the A groups are called the representative elements

Parts of Periodic Table

• Metals: __________ of staircase

• Nonmetals: __________ of staircase

• Metalloids: elements adjacent to staircase (except Al, Po)

The group B are called the transition metals

These are called the inner transition metals and they belong here

Study Buddy Review

• Identify the follow parts of the periodic table:– Halogens

– family

– Alkali metals

– Metals

– Inner transition metals

– Noble gases

– Metalloids

– Period

The Atom

Early Models of the Atom

Atom

• Smallest particle of an element that ____________________________________________________________

Democritus & Kanada

• KanadaAncient Indian philosopher

4 elements

air

fire

earth

water

Made up of tiny particles

• DemocritisGreek Philosopher

~450 BC

Logic

___________________________

Contributing Principles to Idea of Atom

• ____________________________________

• Antoine and Marie Lavoisier

• Conducted controlled experiments and made many quantitative measurements

• Late 1700’shttp://images.search.yahoo.com/search/images/

Contributing Principles to Idea of Atom

• Law of Definite Composition

• A given compound always ______________________________________________________ by mass

• Joseph Louis Proust

• 1799

http://images.search.yahoo.com/search/images/

John Dalton’s Atomic Theory (1803)1. Elements composed of small

particles called _________

2. All atoms of a given element are the same, but different from other elements

3. Atoms ______________

__________________in a chemical reaction

1. Compounds are composed of atoms combined in simple whole number ratios

www.english.upenn.edu/~jlynch/Frank/People/dalton.html - 2k

Study Buddy Review

• Describe the contribution of each towards the historical development of the atom:– Lavoisier

– Proust

– Democritus

– Dalton

What is inside the atom?

J.J. Thomson (1897)• Cathode Ray Tube Experiments

Conclusions:

• Stream of negative particles that have mass

• Named________________

• Atoms are not indivisible

• Found ratio:

(electrical charge of electron)

(mass of electron)

1.76 x 108 coulombs = 1 gram of electrons

Robert Millikan (1909)• Oil Drop

Experiment

Measured ______________________________

• Charge of one electron =

-1.6x10-19C

THUS….

Mass of e- =

9.11x10-28ghttp://webphysics.davidson.edu/Alumni/ToHaynie/OilDrop/oilappa.htm

Rutherford’s experiment• English physicist Ernest Rutherford (1911)• _________________________which can be

made a few atoms thick.– alpha particles: positively charged helium nuclei– A form of radioactivity

• When an alpha particle hits a fluorescent screen, it glows.

How Rutherford explained results

• Atom is ________________________________• Small dense,

positive piece at center. (NUCLEUS)

• Alpha particles are deflected by it if they get close enough.

Credit for Subatomic Particles

• 1897 Thomson discovered the electron– Used cathode ray tube

• (1918) Rutherford named positive charged particle the proton– Goldstein (1886) first discovered positively charged particle using

Cathode-ray tube with perforated cathode

– (1932) James Chadwick– Discovered neutrons

Produced neutrons and their masses

Worked with cloud chambers

Subatomic Particles in Atom

ChargeCharge Real massReal mass Relative Relative massmass

p+p+ 1.67 x 10 1.67 x 10 -24-24 g g 1 amu1 amu

e-e- 9.11 x 10 9.11 x 10 -28-28 g g 1/1840 amu1/1840 amu

nnoo 1.67 x 10 1.67 x 10 -24-24 g g 1 amu1 amu

Study Buddy Review

• Name three subatomic particles.

• Who is credited with discovering each particle?

• Describe the Rutherford Gold Foil Experiment.

Information from Periodic Table

Atomic Number and Atomic Mass

• Chemical Symbol: abbreviation for element name

• Atomic Number: ____________in nucleus of atom (and electrons if neutral)

• Mass Number: __________________in nucleus (whole number)

Isotopes

• Isotopes: atoms with the same # of protons _____________________________

• Shorthand notation:

O168 O17

8

• Average Atomic Mass: weighted avg. mass of atoms found in nature

Models of the Atom

Dalton Model of Atom• Small, indivisible spheres

http://images.search.yahoo.com/search/images/

J.J. Thompson’s Model of Atom• Plum Pudding Model,

1896• Thought an atom was

like plum pudding– Dough was positively

charged– Raisins scattered

throughout the dough were negatively charged

– Didn’t know about neutrons at this time

http://images.search.yahoo.com/search/images/

Rutherford’s Model of the Atom• Rutherford Model, 1911• Thought atom was mostly

empty space– Nucleus in center is dense,

positively charge

– Electrons (negatively charged) are in empty space surrounding nucleus

http://images.search.yahoo.com/search/images/

Bohr’s Model of the Atom• Neils Bohr, 1913• Similar to Rutherford’s

model• Thought atom was

mostly empty space– Nucleus in center is dense,

positively charge

– Electrons move in orbits around the nucleus

http://images.search.yahoo.com/search/images/

(Modern) Quantum Mechanical Model of the Atom

• Heisenberg, Schrodinger, many others, ~1926

• Think atom is mostly empty space– Nucleus in center is

dense, positively charge– Electrons are around the

nucleus– Cannot locate location of

electron at specific time

http://particleadventure.org/particleadventure/frameless/modern_atom.html