Chapter 3 The Atom

____________ (450 B.C.) proposed that all matter is made up of tiny, indivisible particles. (atomos) 3-2

Laws Law of Conservation of Mass: mass is neither ____________ during ordinary chemical rxns or ___________ changes. 3-3

Laws Law of Definite Proportions: compounds contain the same ____________ in exactly the same _____________ by mass regardless of the _______ of the sample or the __________ of the compound. 3-4

Laws Law of Multiple Proportions: If two or more ________________ are composed of the same ____________, the _______ of the masses of the second element combined with a certain _________ of the first element is always a ratio of ______________________. 3-5

Daltons Atomic Theory In 1808 ___________, an English schoolteacher, came up with an atomic theory to explain these laws. Many of the _________ of his theory still hold true today. 3-6

Dalton’s Atomic Theory ~ Each ____________ is composed of atoms. ~ Atoms of a given element are __________, and __________ than those of any other element. ~ A given compound forms by ____________ of two or more different atoms, always in the same _______________________ of atoms. ~ Atoms are neither ________________ in any chemical reaction, only _____________. 3-7

The Structure of the Atom ______: the smallest _________ of an element that ________ the chemical ________ of that element. 3-8

The Discovery of the Electron ___________ (1897) an English physicist who discovered ________ using his famous ___________ experiment. He determined the _______________ ratio. 3-9

The Discovery of the Electron

__________ (1909) an American __________ who determined the charge of electrons using his famous _________ experiment. The mass of an e - is approximately ________ the mass of an atom. 3-11

The Discovery of the Electron

Based on these discoveries, two inferences were made: 1.Because atoms are ____________, they must contain a ________ charge to _________ the negative electrons. 2.Because e- are so light in mass _________ to atoms, atoms must contain other _____________ that account for most of it’s mass. 3-13

Plum Pudding Atomic Model

Discovery of the Nucleus 1911, Ernest ________ conducted experiments with _________ materials that released only __________ charged alpha particles…. 3-15

Discovery of the Nucleus

Rutherford concluded atoms have a ________ core with a _______ charge. Rutherford’s Atomic Model:

Discovery of the Nucleus Rutherford’s student, _________, came up with a way to explain the location of e- in the atom:

Discovery of the Nucleus The electron cloud is the current accepted model of the atom.

The Atom Except for H, all ____________ contain _____________________. A proton has a + charge ____________ _____________to the neg. charged e-. Atoms contain _______________ of p+ and e-. Neutrons are _____________ neutral. P+ and n o have almost ____________ masses, electrons weigh 1836 times ______. 3-20

The Atom ______________: short range p+ to p+, p+ to n o and n o to n o forces hold the nuclear particles together. ___________________ (Z): the number of protons in each atom of a particular element. ☺ The atomic number _________ the element! 3-21

Isotopes __________: atoms of the same element that have _______________ due to different numbers of __________. _____________: the total number of _______ and _________ that make up the nucleus of an isotope ~ Isotopes are written with the _____________ written after the element name or symbol with a _______: ex. Uranium-235 or U

Isotopes Uranium-235 or U-235 Mass number – atomic number = number of ________ 235 (protons + neutrons) – 92 protons = 143 neutrons This info could also be portrayed using a _____________: 235 U 92

Isotopes ~ In nature, __________ are almost always found as a ___________ of isotopes ~ Isotopes have ________________ chemical properties ~Isotopes with _______ neutrons have a higher mass and are often descibed as “_______ ”. 3-24

Isotopes Nuclide: a general term for a _________ __________ of an element.

Atomic Mass Atomic Mass Unit (____): one amu is exactly _____ of the mass of a ________ atom. _______________: the weighted average of the atomic masses of the _________________ isotopes of an element. 3-26

Calculating the Average

Moles _____: the amount of a substance that contains as many _______ as there are atoms in exactly 12g of ___________.

Moles _____________: the number of particles in exactly one ______ of a pure substance ~ x (we’ll use __________)

Moles 602,200,000,00 0,000,000,000, 000 If you had x pennies and gave away 1 million a day to every person on earth, it would take you 3000 years to distribute all your money!! 3-30

Molar Mass ____________: the mass of one mole of a pure substance. ~ the mass of _________ atoms or __________ is measured in _____. The mass of a mole of the same substance is _____________ the same, with the units _______. Ex. H 2 0 = H x 2 = 1.01 x 2 = O x 1 = x 1 =

Molar Mass 1) What is the molar mass of BaCl 2 ? 2) What is the molar mass of NaI? 1) Ba = _ x _____ g/mol = _______ Cl = _ x _____ g/mol = ______ _______ g/mol 2) Na = _ x ______ g/mol = ______ I = _ x _______ g/mol = _______ ________ g/mol 3-31

Molar Mass This photograph shows one mole of _______ (NaCl 58.44g/mol), ____ (H 2 O g/mol), and ____(N g/mol). 3-33

Mass/Mole Conversions When given the number of _______, you can find the _______by: Moles x _g__ = grams mole Ex. 5.0 moles of H 2 O = X g 5.0 moles x 18.02g = 90. g H 2 O in 5.0 molmoles 3-34

Mass/Mole Conversions Moles x _g_ = moles mol Now try these problems: 3) 8.32 moles of barium chloride equals how many grams? 4) 20.1 moles of sulfur dioxide equals how many grams? 3-35

Mass/Mole Conversions 3) 8.32 moles of barium chloride equals how many grams? 8.32 moles BaCl 2 x _____ g/mol = _____ grams BaCl 2 4) 20.1 moles of sulfur dioxide equals how many grams? 20.1 moles SO 2 x ______ g/mol = _____ g SO

Mass/Mole Conversions

When given the amount in _______, you can calculate the number of ______ by: g x mol = moles g Ex g NaCl = X moles ___ g NaCl x 1.0 mol NaCl = _____ mols NaCl 58.44g 3-38

Mass/Mole Conversions g x mol = moles g Now try these problems: 5) g of sodium chloride equals how many moles? 6) g of ammonia equals how many moles? 3-39

Mass/Mole Conversions 5) g of sodium chloride equals how many moles? _______ g NaCl x mole = _____ moles NaCl _____g 6) g of ammonia equals how many moles? _____ g NH 3 x mole = _____ moles NH 3 ______g 3-40

Particle/Mole Conversions You can also calculate between _______ and number of ________: (1.0 moles = x particles) To enter this number into your calculator, punch in _____ button (________)

Particle/Mole Conversions Ex moles of marble (CaCO 3 ) contains how many molecules? _____ mol CaCO 3 x x molecules = ___________ 1.0 mol CaCO 3 molecules *Particles can be molecules, atoms or formula units 7) How many molecules are in 5.0 moles of carbon dioxide? 5.0 mol CO 2 x ________ molecules = 1.0 mole CO 2 __________ molecules CO

Particle/Mass Conversions Ex. What is the mass of 3.25 x10 23 molecules of nitrogen ? 3.25 x10 23 N 2 x 1.0 mol x ______ g = _____g N x mol 8) How many molecules are g of NaCl? g NaCl x 1.0 mol x __________ = __________ ____ g1.0 mol molecules 3-43

The End!