Fall 2011 – Week 5 (Atomic Structure) Chemistry catalysts Fall 2011 – Week 5 (Atomic Structure)

Catalyst (5 min) 9/6/11 Developing Atomic Models EQ: How has mankind’s view of the atom changed over time? Name the three subatomic particles that make up the atom. Describe the properties and location of each part. Draw an atom of Oxygen-17.

Atomic Theory How can we know that these incredibly small, invisible particles exist?

Early Atomic Theory Empedocles (470 BC) Democritus (440 BC) All matter is composed of earth, air, water and fire Democritus (440 BC) Nature consists solely of an infinite number of indivisible particles called atomos (Greek for ‘cannot cut’) Aristotle (250 BC) All matter is composed of earth, air, water and fire, and this matter can be cut in half an infinite number of times This atomic theory prevailed for 2000 years

Early Atomic Theory Elements consist of tiny particles called atoms. John Dalton (1803-1810) Elements consist of tiny particles called atoms. Atoms of the same element are alike in mass and size. Atoms combine to form compounds in simple numerical ratios, such as 1:2, 2:3, etc. Atoms of two elements may combine in different ratios to form more than one compound. (Ex: H2O and H2O2)

Early Atomic Theory Consequences of Dalton’s Law The Law of conservation of Mass/Matter: “There is no detectable change in mass in an ordinary chemical reaction.” The Law of Constant Composition: “A compound always contains the same elements in the same proportions by mass.” The Law of Multiple Proportions: “The masses of one element that combine with a fixed mass of the second element are in a ratio of small whole numbers.”

Joseph John Thomson (1856-1940) Discovered the first subatomic particle, the electron, in1897 using a cathode ray The cathode ray was actually a stream of negatively charged electrons Inside details

J.J. Thomson’s model of the Atom The Plum Pudding Model J.J. Thomson’s model of the Atom Front cover drawing positive negative

Ernest Rutherford (1871 – 1937) Discovered the nucleus in 1913 Only a few of the 8000 positively charged particles shot at the gold foil were deflected or bounced back The Gold Foil experiment showed that the nucleus was small, dense and positively charged Inside details Rutherford went on to discover the proton in 1920 and James Chadwick discovered the neutron is 1932

Rutherford’s Gold Foil Experiment Discuss similarities to the marble activity

Rutherford Gold Foil Experiment http://www.youtube.com/watch?v=Q8RuO2ekNGw

Ernest Rutherford’s model of the atom The Nuclear Atom Ernest Rutherford’s model of the atom Front cover drawing positive negative

Niels Bohr (1885 – 1962) 1913 – Bohr said that the characteristic color of elements could not be explained by earlier models Bohr studied the energy levels of Hydrogen and determined that its electron travels on distinct paths like planetary orbits around the sun. Inside details

Flame Tests Each element has a characteristic color when energy is added. potassium lithium strontium calcium sodium

Planetary Model Niels Bohr’s model of the atom positive negative Front cover drawing positive negative

Notes: Subatomic Particles TextbookPg 97 Copy this table into your notes. Particle Charge Location within atom Relative Size (amu) Mass (kg) Proton +1 Nucleus 1 1.673 x 10-27 Neutron 0 (neutral) 1.675 x 10-27 Electron -1 Outside Nucleus 1/1840 ≈ 0 9.11 x 10-31 amu = atomic mass unit

Catalyst (5 min) Draw this atom. Label its parts. 9/7/11 Protons, Neutrons, & Electrons EQ: How do you determine the number of protons, neutrons, & electrons in atoms? Draw this atom. Label its parts. What element is this?

Vocabulary Li Li Atomic Number 3 Li lithium 6.9 3 Li lithium 6.9 Atomic Number Number of protons in an atom of an element Equals number of electrons in neutral atoms Determines the order of elements in the periodic table

Practice with Atomic # How many protons does an atom of chlorine (Cl) have? How many protons does an atom of potassium (K) have? How many electrons does an atom of (C) have? Which atom has more protons, fluorine (F) or neon (Ne)? 17 19 6 Neon

Vocabulary Isotope An atom of an element with a different mass from another atom of the same element The difference in mass must come from a different number of neutrons because the protons and electrons are the same.

Vocabulary protons + neutrons Mass Number The sum of all the particles in the nucleus of an individual atom protons + neutrons The actual mass of an individual atom This number does NOT appear on the periodic table and is usually not equal to the average atomic mass of the element

Ways to Express Isotopes Hyphen Notation Mass Number Lithium - 7 Li Nuclear Symbol Atomic Number

Ways to Express Isotopes Hyphen Notation Mass Number Li - 7 Li Nuclear Symbol

Calculating Neutrons in Isotopes Lithium-6 Lithium-7 Atomic number of lithium = 3. Both have 3 protons Mass number - protons = neutrons. For Lithium-6, subtract 6-3 to get 3 neutrons For Lithium-7, subtract 7-3 to get 4 neutrons Mass Numbers

Practice with Mass # How many protons and neutrons are there in an atom of carbon-13? How many protons and neutrons are there in an atom of ? How many protons and neutrons are there in an atom of oxygen-18? 6 protons, 7 neutrons , 6 electrons C 6 protons, 8 neutrons , 6 electrons Use before Isotope Practice #1 8 protons, 10 neutrons , 8 electrons

Practice Combine this with Bohr’s Planetary Model of the Atom Nitrogen-15 7 protons 7 electrons 8 neutrons Use before Draw & Name Isotopes 7 p+ 8 n0

Li Vocabulary Review Lithium - 7 Atomic number is… Mass number is… the # of protons found at the top of the periodic table square equal to # of electrons for neutral atoms Mass number is… the # of protons plus the # of neutrons not on the periodic table (must be given) Isotopes are… the same element with different # of neutrons the same element with different mass numbers

Catalyst (5 min) 9/8/11 Isotopes EQ: What are isotopes? Identify the number of protons, neutrons, and electrons in… Uranium-235 O-17 Pb C

Li Vocabulary Review Lithium - 7 Atomic number is… Mass number is… the # of protons found at the top of the periodic table square equal to # of electrons for neutral atoms Mass number is… the # of protons plus the # of neutrons not on the periodic table (must be given) Isotopes are… the same element with different # of neutrons the same element with different mass numbers

Vocabulary Li Li Average Atomic Mass 3 Li lithium 6.9 3 Li lithium 6.9 Average Atomic Mass The weighted average of the masses of all the atoms of an element The periodic table is NOT ordered by atomic masses. For example, check out Co and Ni. More on average atomic mass tomorrow...

Practice What is the atomic mass of chlorine? What is the atomic mass of carbon? Which element has greater atomic mass, potassium or argon? 35.4 amu 12.0 amu argon

Classwork 9/8/11 Matter Neutron Atom Electron Element Atomic number Draw a concept map for the following terms: The details are the most important part! Don’t forget to include them! Matter Neutron Atom Electron Element Atomic number Isotope Atomic mass Proton Mass number

This concept map was made using Cmap Tools, a free software download available online. Try it out!

Matter Electron Atom Atomic number Element Atomic mass Isotope Proton This concept map was made using Cmap Tools, a free software download available online. Try it out! Matter Electron Atom Atomic number Element Atomic mass Isotope Proton Mass number Neutron

Concept Map Note the connections between words Yours may look different from this one!

Li Catalyst (5 min) 9/9/11 Atomic Models Lithium - 7 Catalyst (5 min) 9/9/11 Atomic Models EQ: How can I model the parts of an atom? Count the protons, neutrons, & electrons in these pictures. Name the isotopes using hyphen notation and the nuclear symbol formats.