Atomic Structure Chapter 3

Objectives IV.B.1(a) - Describe the importance of models for the study of atomic IV.B.1(b) - Describe the crucial contributions of scientists and the critical experiments that led to the development of the modern atomic model

Why are models important? Allow visualization Predict how elements and compounds will behave Explain WHY elements and compounds behave the way they do

3.1 - The elements Objectives: Learn the abundances of the elements Learn the names and symbols of commonly used elements 3.1 - The elements

The Elements Profound effects on health Produce ornaments and tools Lithium on manic-depression Cobalt on violent behavior Produce ornaments and tools

All of the materials in the universe can be chemically broken down into about 100 different elements. Compounds are made by combining atoms of the elements just as words are constructed from the letters in the alphabet.

The Greeks 4 elements: 1st to attempt to explain chemical changes Earth Air Fire Water 1st to attempt to explain chemical changes

The Alchemists Magicians/mystics who tried to turn cheap metal to gold Discovered sulfur, mercury, antimony Discovered how to make acids

Robert Boyle Robert Boyle (1627-1691) Recognized importance of careful measurements Properties of gases Science should be firmly grounded in experiments Element cannot be broken down into simpler substances

Relative Abundance Nine elements account for about 98% of the earth’s crust, oceans and atmosphere.

The elements in living matter are very different from those in the earth’s crust. In the human body, oxygen, carbon, hydrogen and nitrogen are the most abundant elements

Names and Symbols for the Elements Each element has a name and a symbol The symbol usually consists of the first one or two letters of the element’s name. First letter capitalized, second letter lower case Examples: Oxygen O Krypton Kr

Names and Symbols for the Elements Sometimes the symbol is taken from the element’s original Latin or Greek name. Examples: gold Au aurum lead Pb plumbum tin Sn stannum silver Ag argentum mercury Hg hydrargyrum iron Fe ferrum

Names and Symbols for the Elements Each element has a name and a symbol. Sometimes the name is taken from the element’s place of discovery Examples: Francium Fr Germanium Ge Sometimes the name is taken from a famous scientist Examples: Einsteinium Es Curium Cm

JJ Thomson & William Thomson’s Atom Discovery of the electron in 1897 Plum pudding model Positively charged sphere with electrons scattered throughout

Rutherford’s Atom (11.1) Showed nucleus was composed of protons and neutrons Rutherford animation (large scale) Rutherford animation (small scale)

Rutherford’s Experiment

Results of Rutherford’s Experiment (a) The results that the metal foil experiment would have yielded if the plum pudding model had been correct (b) Actual results

James Chadwick Discovered the neutron

3.2 – Atoms & compounds OBJECTIVES To learn about Dalton’s theory of atoms To understand and illustrate the law of constant composition To learn how an isotope is written and the number of protons, neutrons and electrons are calculate 3.2 – Atoms & compounds

Law of Constant Composition A given compound always contains the same proportion by mass of the elements of which it is composed Examples:

Dalton’s Atomic Theory All elements are composed of atoms. All atoms of a given element are identical. Atoms of different elements are different. Compounds consist of the atoms of different elements. Atoms are indivisible. Atoms are not created or destroyed in a chemical reaction.

Concept Check Which of the following statements regarding Dalton’s atomic theory are still believed to be true? Elements are made of tiny particles called atoms. All atoms of a given element are identical. A given compound always has the same relative numbers and types of atoms. IV. Atoms are indivisible.

Counting Atoms

Atoms Atomic number = number of protons Atoms are neutral (no charge) Protons = electrons Neutrons = atomic mass – atomic number

POGIL ACTIVITY – ISOTOPES Hg

Key points of Isotopes Key 1 – Key 2 – Key 3 –

Objectives Know the meaning of a chemical formula Know the parts of the periodic table Use the periodic table to identify elements

Formulas of Compounds Atoms shown by chemical symbol Number of each type shown by a subscript to the right of the chemical symbol

Part of the Periodic Table

Objectives Identify and describe a cation and anion Use the periodic table to predict the charge on a cation and anion

Cations Atoms that LOSE electrons More protons than electrons Metals (groups 1 and 2) Transition metals (groups 3-12) Written as superscript after symbol

Metals Group 1 = +1 Group 2 = +2 Ex: sodium = Na+1 Group 2 = +2 Ex: magnesium = Mg+2 Transition metals have charges in parenthesis after name in Roman numerals Ex: lead(II)

Anions Atoms that GAIN electrons More electrons than protons Non-metals Examples - sulfur, phosphorus, fluorine, etc Group 17 = -1 Group 16 = -2 Group 15 = -3 Charge is written as superscript after symbol Ex: Cl-1

Calculating Average Atomic Mass Calculate the average atomic mass of sulfur given the following isotopes and their respective abundances:   Atomic mass % abundance Sulfur-32: 31.972 071 00 94.99% Sulfur-33 32.971 458 76 0.75% Sulfur-34 33.967 866 90 4.25% Sulfur-36 35.967 080 76 0.01%