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Chapter 3 - Atoms: the building blocks of matter. Taken from Modern Chemistry written by Davis, Metcalfe, Williams & Castka. HW – Notes on section 3.1 pgs 65-67. Section 3.1 – The Atom: from philosophical idea to scientific theory. Students will be able to : Explain the laws of

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## Chapter 3 - Atoms: the building blocks of matter

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**Chapter 3 - Atoms: the building blocks of matter**Taken from Modern Chemistry written by Davis, Metcalfe, Williams & Castka**HW – Notes on section 3.1 pgs 65-67**Section 3.1 – The Atom: from philosophical idea to scientific theory • Students will be able to : • Explain the laws of • Conservation of mass • Definite proportion • Multiple proportion • Summarize the 5 essential points of Dalton’s atomic theory • Explain the relationship between the 5 essential points and the above mentioned laws Objectives**Section 3.1 – The Atom: from philosophical idea to**scientific theory As early as 400 B.C.E. particle theory of matter was supported – the particle was called an atom based on the Greek for “indivisible”. Supported by Democritus Aristotle did not believe this theory and his opinion lasted for 2 000 years. Felt all matter was continuous. Foundations of Atomic Theory**Section 3.1 – The Atom: from philosophical idea to**scientific theory By 1700s accepted idea that an element could not be broken down further. Back The transformation of substance or substances into one or more new substances was known as a chemical reaction. Foundations of Atomic Theory (continued) By the 1790s there was a new emphasis on quantitative analysis of chemical reactions**Section 3.1 – The Atom: from philosophical idea to**scientific theory This work lead to the discovery of several laws. . . Law of Conservation of matter which states that mass is neither destroyed or created during ordinary chemical or physical reactions. Foundations of Atomic Theory (continued) Antoine Lavoisier Back**The law of definite proportions, sometimes called Proust's**Law, states that a chemical compound always contains exactly the same proportion of elements by mass. Section 3.1 – The Atom: from philosophical idea to scientific theory Foundations of Atomic Theory (continued) Book example: salt is always 39.34% Na (sodium) and 60.66% Cl (Chlorine) by mass Joseph Proust**The law of multiple proportions, statement that when two**elements combine with each other to form more than one compound, the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers. Section 3.1 – The Atom: from philosophical idea to scientific theory You Tube Help Foundations of Atomic Theory (continued) Rethink value of video Back**1.All matter is made of extremely small particles called**atoms. Relationship Section 3.1 – The Atom: from philosophical idea to scientific theory 2.All atoms of the same element are identical in size, mass & other properties. Relationship Dalton’s Atomic Theory 3.Atoms cannot be subdivided, created or destroyed. Relationship 4.Atoms of different elements combine in WHOLE-number ratios to form compounds. 5.In chemical reactions atoms are combined, separated or rearranged. Relationship**Dalton turned idea’s (of ancient Greeks) into scientific**theory Section 3.1 – The Atom: from philosophical idea to scientific theory Today we know that atoms can be divided, but the law of conservation of matter holds true still. Modern Atomic Theory**Section 3.1 – The Atom: from philosophical idea to**scientific theory Quiz Break**HW – Notes on section 3.2 pgs 70-74**• Students will be able to : • Summarize the observed properties of cathode rays that led to the discovery of the electron. • Summarize the experiment carried out by Rutherford and his co-workers that led to the discovery of the nucleus. • List the properties of protons, neutron and electrons • Define atom. Section 3.2 – The Structure of the Atom Objectives**1st discovery of a subatomic particle resulted from**investigations into the relationship between electricity and matter. Section 3.2 – The Structure of the Atom Discovery of the Electron**Hypothesized that the glow was caused by a stream of**particles which they called a cathode ray. Section 3.2 – The Structure of the Atom Tested and found that An object placed between the cathode ray and the opposite end casts a shadow. A paddle wheel placed on rails rolled toward the anode from the cathode. Discovery of the Electron - Cathode Rays and Electrons Don’t forget hyperlink**This supported the idea of a cathode ray. . .**Section 3.2 – The Structure of the Atom Further testing found that Cathode rays were deflected by a magnetic field. Deflected away from negatively charged objects. Discovery of the Electron - Cathode Rays and Electrons (continued) Thompson hypothesized that the ray was a particle, a negative one – later named electrons.**Thompson’s work showed that the electron has a very large**charge for its tiny mass Section 3.2 – The Structure of the Atom R. A. Millikan (right) showed the mass to be 9.109 x 10-31 kg Charge and Mass of the electrons**Based on that information two more inferences were made**about atomic structure. Section 3.2 – The Structure of the Atom Atoms are electrically neutral so there must be positively charged particles to balance out the negative electron. Because electrons have so much less mass than atoms, atoms must contain other particles which account for most of their mass. Charge and Mass of the electrons – (continued)**Ernest Rutherford & associates bombarded a thin gold foil**with alpha particles (+ charge & 4 x mass of H atom) • Expected most particles to pass through with slight deflection – shocked to find that 1 in 8 000 were redirected back toward source. Section 3.2 – The Structure of the Atom Discovery of the Atomic Nucleus**Rutherford reasoned that the bounce back was from a densely**packed bundle with a positively bundle he called the nucleus. Section 3.2 – The Structure of the Atom If the nucleus were the size of a marble the atom would be the size of a football field Discovery of the Atomic Nucleus – (continued)**Except for the simplest type of hydrogen all atomic nuclei**are made of two types of particles, protons and neutrons. Section 3.2 – The Structure of the Atom Composition of the Atomic Nucleus Protons have a (+) charge which balances out the charge of the electrons. Mass = 1.673 x 10-27 kg Neutrons have a no charge and a mass = 1.675 x 10-27 kg**Nuclei of atoms of different elements differ in the # of**protons they contain and therefore in the amount of positive charge. Section 3.2 – The Structure of the Atom Composition of the Atomic Nucleus – (continued)**e**n H 0 1 1 -1 0 1 Section 3.2 – The Structure of the Atom Properties Summarized * 1 amu (atomic mass unit) = 1.660 540 x 10-27 kg**Like forces generally repel one another however when two**protons are extremely close there is a strong attractions Section 3.2 – The Structure of the Atom These short-range proton-neutron, proton-proton, and neutron-neutron forces hold the particles together and a referred to as nuclear forces. Composition of the Atomic Nucleus - Forces in the Nucleus**Atomic radii range from 40 to 270 pm (picometers)**• Where as the nuclei of atoms have a much smaller radii • About 0.001 pm Section 3.2 – The Structure of the Atom The sizes of Atoms**HW – Notes on section 3.3 pgs 75-80**• Students will be able to : • Explain what isotopes are. • Define atomic number and mass number, and describe how they apply to isotopes. • Given the identity nuclide, determine its number of protons, neutrons and electrons. Section 3.3(A) – Counting Atoms Objectives**The atomic number of an element is the number of protons in**the nucleus of each atom of that element Section 3.3(A) – Counting Atoms Atomic Number**Isotopes are atoms of the same element that have different**masses. All hydrogen contain the same number of protons but may contain different number of neutrons. Section 3.3(A) – Counting Atoms Isotopes**The mass number is the total number of protons and neutrons**in the nucleus of an isotope. Section 3.3(A) – Counting Atoms Mass Number**Section 3.3(A) – Counting Atoms**Isotopes Are all atoms of an element alike? Isotopes - pogil**Section 3.3(A) – Counting Atoms**Isotopes of “Pennium” Isotopes – Pennium Lab**Nuclide is a general term for any isotope of any element.**Section 3.3(A) – Counting Atoms S = element’s symbol Nuclear Symbol a = protons + neutrons Designating Isotopes 80 a S Br b = protons 35 b Protons = ______ Neutrons = _______ Electrons = ________ Bromine has Practice Practice Key**The standard used by scientist to govern units of atomic**mass is the carbon-12 nuclide. One atomic mass unit , or amu is exactly 1/12th the mass of a carbon-12 atom, or 1.660 540 x 10-27 kg Although isotopes may have different masses, they do not differ significantly in their chemical behavior. Section 3.3(A) – Counting Atoms Relative Atomic Masses**Averageatomic mass is the weighted average of the atomic**masses of the naturally occurring elements. Section 3.3(A) – Counting Atoms Example with marbles (100 total) 25 marbles x 2.00 g = 50 g 75 marbles x 3.00 g = 225 g Adding the masses gives 50 g + 225 g = 275 g Divide this by the total number of marbles and you get an average marble mass of 2.75 g Average Atomic Masses of Elements**Section 3.3(A) – Counting Atoms**Averageatomic mass How are the masses on the periodic table determined? Average Atomic Masses of Elements –(continued) (KEY)**HW – Notes on section 3.3 pgs 80-85**• Students will be able to : • Define mole in terms of Avogadro’s number, and define molar mass. • Solve problems involving mass in grams, amount in moles and number of atoms of an element. Section 3.3(B) – Counting Atoms Objectives**A mole (abbreviated mol)is the amount of a substance that**contains as many particles as there are atoms in exactly 12 g of carbon-12. Section 3.3(B) – Counting Atoms Relating Mass to Numbers of Atoms-the Mole**The number of particles in a mole has been experimentally**determined in a number of ways. Avogadro’s number 6.011 1367 x 1023– is the number of particles in exactly one mole of a pure substance. For ours (and most purposes) Avogadro’s number is rounded to 6.022 x 1023 Section 3.3(B) – Counting Atoms Relating Mass to Numbers of Atoms–Avogadro’s number It is a big number!**The alternative definition of mole is the amount of**substance that contains avogadro’s number of particles. The mass of one mole of a pure substance is called the molar mass of that substance.Usually written in units of g/mol. Section 3.3(B) – Counting Atoms Relating Mass to Numbers of Atoms–Molar Mass**There are 3 mole equalities. They are:**1 mol = 6.02 x 1023 particles 1 mol = g-formula-mass (periodic table) 1 mol = 22.4 L for a gas at STP* Section 3.3(B) – Counting Atoms Relating Mass to Numbers of Atoms–Gram/Mole Conversions * STP = 0° C & 1 atm Pressure**There are 3 mole equalities. They are:**1 mol = 6.02 x 1023 particles 1 mol = g-formula-mass (periodic table) 1 mol = 22.4 L for a gas at STP* Section 3.3(B) – Counting Atoms These become. . . [----] OR [----] [-------------] or [-------------] 1 mol [-------------] or [-------------] 1 mol 6.02 x 1023 particles 22.4 L 1 mol g-formula-mass (periodic table) 22.4 L 1 mol 1 mol 6.02 x 1023 particles g-formula-mass (periodic table) 1 mol Relating Mass to Numbers of Atoms– Conversions**There are 3 mole equalities. They are:**1 mol = 6.02 x 1023 particles 1 mol = g-formula-mass (periodic table) 1 mol = 22.4 L for a gas at STP* Reference Sheet These become. . . [-------------] or [-------------] [----] OR [----] 1 mol [-------------] or [-------------] 1 mol 6.02 x 1023 particles 22.4 L 1 mol g-formula-mass (periodic table) 22.4 L 1 mol 1 mol 6.02 x 1023 particles g-formula-mass (periodic table) 1 mol**g-formula-mass (periodic table)**For a single element it is simply the atomic mass found on the periodic chart Section 3.3(A) – Counting Atoms Relating Mass to Numbers of Atoms– What does it mean?**g-formula-mass (periodic table)**N Section 3.3(A) – Counting Atoms Ca Relating Mass to Numbers of Atoms– Examples Ag Ba**g-formula-mass (periodic table)**For a COMPOUND you will need to calculate using atomic mass found on the periodic chart Section 3.3(A) – Counting Atoms Relating Mass to Numbers of Atoms– What does it mean?**g-formula-mass (periodic table)**COMPOUNDS Section 3.3(B) – Counting Atoms Table Salt NaCl Water H2O Relating Mass to Numbers of Atoms– EXAMPLE Sugar (glucose) C6H12O6**g-formula-mass (periodic table)**COMPOUNDS inorganic salt (soil fertilizer) (NH4)2SO4 Section 3.3(B) – Counting Atoms Relating Mass to Numbers of Atoms– EXAMPLE**Practice 1**Section 3.3(B) – Counting Atoms Relating Mass to Numbers of Atoms– MOLE PRACTICES Practice 2 Practice 2 (Key)**Given : 2.860 m ceiling height**9.630 m room depth 10.620 m room width Section 3.3(B) – Counting Atoms • Atmosphere composition: • Nitrogen - 78.084%Oxygen - 20.95% • 1 000 L = 1 m3 Relating Mass to Numbers of Atoms– FUN WITH MOLES How many mols of O2 and N2 are present in this room?**Atmosphere composition:**Nitrogen - 78.084%Oxygen - 20.95% Section 3.3(B) – Counting Atoms Relating Mass to Numbers of Atoms– FUN WITH MOLES How many particles of O2 and N2 are taken in with each breath?**Relax**Look for things you recognize Estimate size of final answer (with this comes do I remember using any of these before) Set up and work out Double check with estimate and your sig figs Section 3.3(B) – Counting Atoms Relating Mass to Numbers of Atoms– suggestions**Practice 3**Practice 3 (KEY) Section 3.3(B) – Counting Atoms TAKE-HOME QUIZ (KEY) TAKE-HOME QUIZ Relating Mass to Numbers of Atoms– MORE MOLE PRACTICES Practice 4 Practice 4 (KEY)

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