Atomic Structure Timeline

Democritus (400 B.C.) Proposed that matter was composed of tiny indivisible particles Not based on experimental data Greek: atomos

Alchemy (next 2000 years) Mixture of science and mysticism. Lab procedures were developed, but alchemists did not perform controlled experiments like true scientists.

John Dalton (1807) British Schoolteacher Billiard Ball Model based his theory on others’ experimental data Billiard Ball Model atom is a uniform, solid sphere

John Dalton Dalton’s Four Postulates 1. Elements are composed of small indivisible particles called atoms. 2. Atoms of the same element are identical. Atoms of different elements are different. 3. Atoms of different elements combine together in simple proportions to create a compound. 4. In a chemical reaction, atoms are rearranged, but not changed.

Henri Becquerel (1896) Discovered radioactivity Three types: spontaneous emission of radiation from the nucleus Three types: alpha () - positive beta () - negative gamma () - neutral

J. J. Thomson (1903) Cathode Ray Tube Experiments Discovered Electrons beam of negative particles Discovered Electrons negative particles within the atom Plum-pudding Model

J. J. Thomson (1903) Plum-pudding Model positive sphere (pudding) with negative electrons (plums) dispersed throughout

Ernest Rutherford (1911) Gold Foil Experiment Discovered the nucleus dense, positive charge in the center of the atom Nuclear Model

Gold Foil Experiment Alpha particles shot through gold foil. Most went straight through. A few were deflected because the particle hit the nucleus of the gold foil.

Ernest Rutherford (1911) Nuclear Model dense, positive nucleus surrounded by negative electrons

Niels Bohr (1913) Bright-Line Spectrum Energy Levels Planetary Model tried to explain presence of specific colors in hydrogen’s spectrum Energy Levels electrons can only exist in specific energy states Planetary Model

Niels Bohr (1913) Bright-line spectrum Planetary Model electrons move in circular orbits within specific energy levels

Niels Bohr Brightline spectrum

Erwin Schrödinger (1926) Quantum mechanics Electron cloud model electrons can only exist in specified energy states Electron cloud model orbital: region around the nucleus where e- are likely to be found

Electron Cloud Model (orbital) Erwin Schrödinger (1926) Electron Cloud Model (orbital) dots represent probability of finding an e- not actual electrons

James Chadwick (1932) Discovered neutrons Joliot-Curie Experiments neutral particles in the nucleus of an atom Joliot-Curie Experiments based his theory on their experimental evidence

revision of Rutherford’s Nuclear Model James Chadwick (1932) Neutron Model revision of Rutherford’s Nuclear Model

Structure of the Atom Chemical Symbols Subatomic Particles Atomic Structure Structure of the Atom Chemical Symbols Subatomic Particles

Metal that forms bright blue solid compounds. A. Chemical Symbols Capitals matter! Element symbols contain ONE capital letter followed by lowercase letter(s) if necessary. Metal that forms bright blue solid compounds. Co vs. CO Poisonous gas.

B. Subatomic Particles in a neutral atom Most of the atom’s mass. NUCLEUS ELECTRONS in a neutral atom PROTONS NEUTRONS NEGATIVE CHARGE POSITIVE CHARGE NEUTRAL CHARGE Most of the atom’s mass. Atomic Number equals the # of...

B. Subatomic Particles 3 quarks = 1 proton or 1 neutron Quarks He 6 types He 3 quarks = 1 proton or 1 neutron

II. Electron Cloud Model Orbital Energy Levels Bohr Model Diagrams Ch. 10 - Atomic Structure II. Electron Cloud Model Orbital Energy Levels Bohr Model Diagrams

A. Orbital Can’t pinpoint the location of an electron. Region where there is 90% probability of finding an electron. Can’t pinpoint the location of an electron. Density of dots represents degree of probability.

A. Orbital Orbitals have different shapes.

B. Energy Levels Electrons can only exist at certain energy levels. Low energy levels are close to the nucleus. Each energy level (n) can hold 2n2 electrons.

C. Bohr Model Diagrams Simplified energy levels using Bohr’s idea of circular orbits. Can replace with: 3p 4n Lithium Atomic #: 3 Mass: 7 # of p: 3 # of e: 3 # of n: 4 e- e- p n Maximum e- Level 1 2e- Level 2 8e- Level 3 18e- Level 4 32e- e-

III. Masses of Atoms Atomic Mass Mass Number Isotopes Atomic Structure III. Masses of Atoms Atomic Mass Mass Number Isotopes

A. Atomic Mass 1 proton = 1 u 1 neutron = 1 u 1 u = 1.67  10-24 g atomic mass unit (u or amu) 1 u = 1/12 the mass of a 12C atom 1 proton = 1 u 1 neutron = 1 u 1 u = 1.67  10-24 g © Addison-Wesley Publishing Company, Inc.

B. Mass Number Always a whole number. Sum of the protons and neutrons in the nucleus of an atom. © Addison-Wesley Publishing Company, Inc. Always a whole number. # of neutrons = mass # - atomic #

C. Isotopes Mass # Atomic # Isotope symbol or Nuclear Symbol: Atoms of the same element with different numbers of neutrons. Isotope symbol or Nuclear Symbol: Mass # Atomic # “Carbon-12”

Practice Element Nuclear Hyphen Symbol Notation Magnesium Cobalt

Practice There are three isotopes of the element carbon: Carbon-12 The numbers 12, 13,14 represent what?

C. Isotopes © Addison-Wesley Publishing Company, Inc.

C. Isotopes Average Atomic Mass reported on Periodic Table weighted average of all isotopes Avg. Atomic Mass

C. Isotopes EX: About 8 out of 10 chlorine atoms are chlorine-35. Two out of 10 are chlorine-37. Avg. Atomic Mass 35.4 u

Families of Elements Elements are classified into three categories A. Metals Shiny solids; good conductors of heat and electricity

B. Nonmetals all found on the right side of the periodic table (except for Hydrogen) Can be solids, liquids, or gases

Semiconductors or metalloids non metals that can conduct heat and electricity

I. History of the Periodic Table Mendeleev Mosely Ch. 10 - The Periodic Table I. History of the Periodic Table Mendeleev Mosely

A. Dmitri Mendeleev Organized elements by increasing atomic mass. Dmitri Mendeleev (1869, Russian) Organized elements by increasing atomic mass. Predicted the existence of undiscovered elements.

B. Henry Mosely Organized elements by increasing atomic number. Henry Mosely (1913, British) Organized elements by increasing atomic number. Fixed problems in Mendeleev’s arrangement.

II. Organization Metallic Character Rows & Columns Table Sections Ch. 10 - The Periodic Table II. Organization Metallic Character Rows & Columns Table Sections

A. Metallic Character Metals Nonmetals Metalloids

B. Table Sections Representative Elements Transition Metals Inner Transition Metals

B. Table Sections Overall Configuration Lanthanides - part of period 6 Actinides - part of period 7

C. Columns & Rows Group (Family) Period

III. Periodic Trends Terms Periodic Trends Dot Diagrams Ch. 10 - The Periodic Table III. Periodic Trends Terms Periodic Trends Dot Diagrams

A. Terms Periodic Law Properties of elements repeat periodically when the elements are arranged by increasing atomic number.

A. Terms First Ionization Energy Valence Electrons e- in the outermost energy level First Ionization Energy energy required to remove an e- from a neutral atom

B. Periodic Trends Atomic Radius Increases to the LEFT and DOWN.

B. Periodic Trends Increases to the RIGHT and UP. First Ionization Energy Increases to the RIGHT and UP.

Be or Ba Ca or Br Ba Ca B. Periodic Trends Which atom has the larger radius? Be or Ba Ca or Br Ba Ca

N or Bi Ba or Ne N Ne B. Periodic Trends Which atom has the higher 1st I.E.? N or Bi Ba or Ne N Ne

B. Periodic Trends Group # = # of valence e- (except He) Families have similar reactivity. Period # = # of energy levels 1A 2A 3A 4A 5A 6A 7A 8A

C. Dot Diagrams Dots represent the valence e-. EX: Sodium EX: Chlorine

Families of elements

Families of elements Group one: Alkali Metals - Soft, shiny, reacts violently with water - Has one valence electron that can be easily removed to form a cation Example: Sodium ( Na+ )

Families of elements Group 2:Alkaline earth metals - have 2 valence electrons - do not react as violently - will give up 2 electrons and make a cation Example: Calcium ( Ca2+ )

Chapter 4: Families of elements

Families of elements Group 13 (3A) is the Boron Family - This group is a mixture of metalloids and metals -Have 3 valence electrons

Families of elements Group 14 (4A) is the Carbon Family - This group is a mixture of metals, nonmetals and metalloids - Have 4 valence electrons

Families of elements Group 15 (5A) is the Nitrogen Family - This family is a mixture of metals, nonmetals, and metalloids - Have 5 valence electrons

Families of elements Group 16 (6A) is the Oxygen Family - This group has 6 valence electrons - This family is a mixture of metals, nonmetals, and metalloids

Families of elements Group 17 (7A) are the Halogens This group is very reactive. This group is all nonmetals and has 7 valence electrons. Nonmetals gain electrons to form negative ions called anions. Example: Chlorine (Cl- )

Families of elements Group 18 (8A) are the Noble Gases This group has 8 valence electrons They exist as single atom gases. They are un-reactive.