Dalton Model of the Atom.ppt
- 1. Foundations of Atomic Theory Law of Definite Proportions The fact that a chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound. Law of Multiple Proportions If two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first elements is always a ratio of small whole numbers. Law of Conservation of Mass Mass is neither destroyed nor created during ordinary chemical reactions.
- 2. Conservation of Atoms John Dalton Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 204 2 H2 + O2 2 H2O 4 atoms hydrogen 2 atoms oxygen 4 atoms hydrogen 2 atoms oxygen H H O O O O H H H H H H H2 H2 O2 H2O H2O +
- 3. Legos are Similar to Atoms Lego's can be taken apart and built into many different things. H H O O O O H H H H H H H2 H2 O2 H2O H2O + Atoms can be rearranged into different substances.
- 4. 45 g H2O ? g H2O Conservation of Mass Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 204 High voltage Before reaction electrodes glass chamber 5.0 g H2 80 g O2 300 g (mass of chamber) + 385 g total H2 O2 High voltage After reaction 0 g H2 40 g O2 300 g (mass of chamber) + 385 g total O2 H2O
- 5. Law of Definite Proportions Joseph Louis Proust (1754 – 1826) • Each compound has a specific ratio of elements • It is a ratio by mass • Water is always 8 grams of oxygen for every one gram of hydrogen
- 6. The Law of Multiple Proportions • Dalton could not use his theory to determine the elemental compositions of chemical compounds because he had no reliable scale of atomic masses. • Dalton’s data led to a general statement known as the law of multiple proportions. • Law states that when two elements form a series of compounds, the ratios of the masses of the second element that are present per gram of the first element can almost always be expressed as the ratios of integers. Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
- 7. Daltons Atomic Theory • Dalton stated that elements consisted of tiny particles called atoms • He also called the elements pure substances because all atoms of an element were identical and that in particular they had the same mass.
- 8. Dalton’s Atomic Theory 1. All matter consists of tiny particles. Dalton, like the Greeks, called these particles “atoms”. 2. Atoms of one element can neither be subdivided nor changed into atoms of any other element. 3. Atoms can neither be created nor destroyed. 4. All atoms of the same element are identical in mass, size, and other properties. 6. In compounds, atoms of different elements combine in simple, whole number ratios. 5. Atoms of one element differ in mass and other properties from atoms of other elements.
- 10. Daltons’ Models of Atoms Carbon dioxide, CO2 Water, H2O Methane, CH4