Dalton Model of the Atom : Dalton Model of the Atom Late 1700’s - John Dalton- England
Teacher- summarized results of his experiments and those of other’s
Combined ideas of elements with that of atoms in Dalton’s Atomic Theory Foundations of Atomic Theory : 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. Conservation of Atoms : 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 Legos are Similar to Atoms : Legos are Similar to Atoms Legos can be taken apart and built into many different things. Atoms can be rearranged into different substances. Conservation of Mass : 45 g H2O ? g H2O Conservation of Mass Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 204 Before reaction electrodes glass
chamber 5.0 g H2 80 g O2 300 g (mass
of chamber) + 385 g total H2 O2 Law of Definite ProportionsJoseph Louis Proust (1754 – 1826) : Law of Definite ProportionsJoseph 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 Law of Definite Proportions : Law of Definite Proportions 103 g of
copper carbonate 53 g of
copper 40 g of oxygen 10 g of carbon + + Whether synthesized in the laboratory or obtained from
various natural sources, copper carbonate always has
the same composition.
Analysis of this compound led Proust to formulate
the law of definite proportions. Law of Multiple ProportionsJohn Dalton (1766 – 1844) : Law of Multiple ProportionsJohn Dalton (1766 – 1844) If two elements form more than one compound, the ratio of the second element that combines with 1 gram of the first element in each is a simple whole number.
e.g. H2O & H2O2
water hydrogen peroxide
Ratio of oxygen is 1:2 (an exact ratio) What? : What? Water is 8 grams of oxygen per gram of hydrogen.
Hydrogen peroxide is 16 grams of oxygen per gram of hydrogen.
16 g to 8 g is a 2:1 ratio
True, because you have to add a whole atom, you can’t add a piece of an atom. Daltons Atomic Theory : 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. Dalton’s Theory Continued : Dalton’s Theory Continued He also said the reason why elements differed from one another was that atoms of each element had different masses.
He also said that compounds consisted of atoms of different elements combined together.
Dalton's model was that the atoms were tiny, indivisible, indestructible particles and that each one had a certain mass, size, and chemical behavior that was determined by what kind of element they were. Structure of Atoms : Structure of Atoms Scientist began to wonder what an atom was like.
Was it solid throughout with no internal structure or was it made up of smaller, subatomic particles?
It was not until the late 1800’s that evidence became available that atoms were composed of smaller parts. Dalton’s Symbols : Dalton’s Symbols John Dalton
1808 Daltons’ Models of Atoms : Daltons’ Models of Atoms Dalton’s Atomic Theory : Dalton’s Atomic Theory All matter consists of tiny particles.
Dalton, like the Greeks, called these particles “atoms”. Atoms of one element can neither be subdivided nor changed into atoms of any other element. Atoms can neither be created nor destroyed. 4. All atoms of the same element are identical in mass, size, and other properties. In compounds, atoms of different elements combine in simple, whole number ratios. Atoms of one element differ in mass and other properties from atoms of other elements. Dalton’s Atomic Theory : Dalton’s Atomic Theory 1. All matter is made of tiny indivisible particles called atoms.
2. Atoms of the same element are identical, those of different atoms are different.
3. Atoms of different elements combine in whole number ratios to form compounds
4. Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed. California WEB