Environmental Chemistry Unit 2 Materials: Structure and Uses

Coin Design Competition How are coins made? m?action=vtShellhttp:// m?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 Chemical Changes 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 Review Classify 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 ElementsPeriodic Table of Elements

Dobereiner’s Triads THE LAW OF TRIADS: The atomic mass of the middle element of the triad is equal to the ________________________ of the other two elements. EXAMPLE: Lithium Atomic Mass of 7 Sodium Atomic Mass of 23 Potassium 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 high massed elements such as F, Cl, and Br. 3) As techniques improved for measuring atomic masses accurately, the law became obsolete. Dobereiner’s research made chemists look at groups of elements with similar chemical and physical properties.

Newland’s Law of Octaves When placed in increasing order of their atomic masses, every __________________________ and _________________________. LiBeBCNOF NaMgAlSiPSCl K Ca

Problems with Newland’s Law of Octaves 1) It was not valid for elements that had atomic masses higher than Ca. 2) When more elements were discovered (Noble gases) they could not be accommodated in his table. However, the modern periodic table does draw from the concept 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 be accommodated within the table. 2) In order to make the elements fit the requirements, Mendeleev was forced to put an element of slightly higher atomic weight ahead of one of slightly lower atomic weight.

Henry Moseley ( ) 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 2A3A4A5A6A 7A 8A 0 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 u 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 Kanada Ancient Indian philosopher 4 elements air fire earth water Made up of tiny particles Democritis Greek Philosopher ~450 BC Logic ___________________________

Contributing Principles to Idea of Atom __________________ Antoine and Marie Lavoisier Conducted controlled experiments and made many quantitative measurements Late 1700’s

Contributing Principles to Idea of Atom Law of Definite Composition A given compound always __________________ __________________ __________________ by mass Joseph Louis Proust

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 - 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 10 8 coulombs = 1 gram of electrons

Robert Millikan (1909) Oil Drop Experiment Measured _______________ _______________ Charge of one electron = -1.6x C THUS…. Mass of e - = 9.11x g

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 Charge Real mass Relative mass p x g 1 amu e x g 1/1840 amu nononono 1.67 x g 1 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: O 16 8 O 17 8 Average Atomic Mass: weighted avg. mass of atoms found in nature

Models of the Atom

Dalton Model of Atom Small, indivisible spheres

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

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

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

(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