1Atoms, Ions, and Molecules: The Building Blocks of MatterOverview:1. Dalton’s Atomic Theory2. History of the Atomic Structure3. Structure of the Atom4. Nuclear Chemistry: Balancing Nuclear Equations5. Ions6. Average Atomic Mass7. Molecular Weight (Formula Mass)8. Mole9. Empirical Formula vs Molecular FormulaSuggested Readings:1.Chapter 22.Chapter 6.1 – 6.23.Chapter 20.1 – 20.3
1. Dalton’s Atomic Theory2•Infinitely divisible(Plato/Aristotle)•Ultimate particle (indivisible)–Upon division, eventually aparticle is reached which canno longer be divided. It iscalled “atom”- Democritus(400 BC)“Nothing exists except atoms and empty space; everythingelse is opinion.” - Democritus 460–370 B.C.
3Dalton’s Atomic Theory1. All matter is made up of atoms2. Atoms can neither be created nor destroyed3. Atoms of a particular element are alikeTiny, hard, indivisible particlesAtoms are unchanged in chemical reactionsAll P atoms have the same size, mass and properties4. Atoms of different elements are different from one anotherPb (lead) is different from Au (gold) in size, mass and properties5. A chemical reaction involves either the union or the separation ofindividual atomsCH4(g) + 2 O2(g) → CO2(g)+2 H2O(g)
2. History of the Atomic Structure. What do Atoms look like?
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5Rutherford’s α-particle Experiment- nucleus is small andmassive- atoms are mostly openspaceRutherford’s quote:“It was … as if you fired a 15-inch shell at apiece of tissue paper and it came back and hityou.”α-particles are very small, fast, positivelycharged, and very dense. Few α-particles weredeflected and some were reflected.“Nucleus”“Atom”~10–10m~10–15m
63. Structure of the AtomAtomic number (Z)•# of protons contained in the nucleus of a particular element•# of electrons = # number of protons (for a neutral atom)•determines atom’s characteristics•found on theperiodic table•H, 1 proton; C, 6 protons.Mass number (A)•# of protons (Z) plus the # of neutrons (N):A=Z+N•# of neutrons varies within the same element (ISOTOPES), thusAvaries.C126This isotope of carbon is called 'carbon-12'represents carbonZ: carbon contains 6 protonsA=mass numberN=A–Z= 12 – 6 =6 neutrons
7Example #1Na2311Problem:Identify the mass number, atomic number, number of protons,number of neutrons, and the number of electrons.