CHM160 Ch 2 FA16 S - Chapter 2 Overview Preliminary atomic...

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1 1 CHM 160.2 – Biagioni – FA15 Chapter 2 – Atoms and Elements These represent the overheads used in class, but the are NOT complete class notes. They are provided as a supplement to, not replacement for, class attendance. 2 Preliminary atomic model o Understand how early atomic models developed Nuclei and isotopes o Understand basic atomic substructure, nuclear model Atoms and ions o Understand atoms and ions based on protons and electrons Periodic Table o Introduce PT, arrangement of elements, key groups of elements, relationship to common ions Atomic masses o Introduce atomic mass scale, atomic masses of elements “Counting” atoms o Associate element mass number of atoms Chapter 2 Overview Reading: Chapter 2 (all) 3 Chapter 2 – Key objectives Nuclear model for the atom. Understanding of the observations and key concepts that led to development of the modern view of the atom (includes basic atomic structure, subatomic particles, and isotopes). Ions. Understanding of how ions can be formed from atoms by electron gain or loss. Element names and symbols. Learn names and symbols of a variety of elements. Periodic Table. Understand how the PT was developed and how it organizes elements on the basis of recurring properties. Atomic mass and mole concept. Understand the relationship between atomic scale atomic masses and moles. Be able to use mole concept in calculations (including calculations of numbers of atoms). 4 The old days… Aristotle’s view of matter… . wikispaces.com 5 Development of Dalton’s Atomic Theory (2.2 – 2.3) Developments: o Good quantitative measurements o Law of Conservation of Mass ° Mass neither created nor destroyed in chemical reactions. – Antoine Lavoisier 10.00 g mercuric oxide heat 9.44 g mercury + 0.56 g oxygen 6 Development of Dalton’s Atomic Theory (2.2 – 2.3) Developments: o Concepts of “elements” (building blocks) versus compounds (combinations) o Chemical analysis: how much of each element in compound?
2 7 Observation of “Law of Definite Proportions” (“Constant Composition”) for pure compounds: ° The composition (proportion of elements) of a pure compound will be constant (definite), no matter what the compound’s source is or how it was prepared. – Joseph Proust 8 Additional observation: Pair of elements often formed more two or more distinct compounds. o Nitrogen and oxygen: ° 3 distinct common compounds o Copper and chlorine: ° 2 distinct common compounds o …. Law of Multiple proportions (Dalton): o When two elements (A and B) form two different compounds, masses of B that combine with 1 g A can be expressed as a ratio of small whole numbers. (Tro) 9 Examples: two distinct Cu – Cl compounds Pure Cu – Cl compound Sample Sample mass (g) g Cu g Cl A 5.32 3.42 1.90 B 4.22 1.99 2.23 See Tro: Example and Practice 2.2 10 Law of Multiple Proportions: o Other examples: ° CO and CO 2 ° CuO and Cu 2 O ° NO and NO 2 and N 2 O ° FeO and Fe 2 O 3 and Fe 3 O 4 o Key:

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