Dalton's Atomic Theory And Laws of Proportions

Dalton’s Atomic Theory provides a…

Microscopic explanation of the many macroscopic properties of matter.

Dalton’s Atomic Theory #1 (according to textbook)

Matter is composed of small, indestructible particles called atoms; the smallest unit that can participate in a chemical reaction. (Remember that atoms can be split, and are not the smallest, subatomic particles are, which make up an atom).

Dalton’s Atomic Theory #2 (according to textbook)

An element consists of only 1 type of atom, which has a mass that is characteristic of the element and is the same for all atoms of that element. Plus, all the properties are the same. EX: All gold atoms have the same mass and share the same chemical properties, and a gold atom is different from any other type of atom, like a carbon atom, which has its own unique mass and properties.

Dalton’s Atomic Theory #3 (according to textbook)

Atoms of one element differ in properties from atoms of other elements. EX: Gold atoms behave differently than silver atoms do.

Dalton’s Atomic Theory #4 (according to textbook)

A compound consists of atoms of two or more elements combined in a small, whole-number ratio. In a given compound, the numbers of atoms of each of its elements are always present in the same ratio. EX: CO2 ratio is 1:2. or C8H18 ratio is C8:H18.

Dalton’s Atomic Theory #5 (according to textbook)

Atoms are neither created nor destroyed during a chemical reaction, but are rearranged to give substances that are different from those present before the reactions. EX: CH4 + 2O2 = CO2 + 2H2O.

Matter is neither…

Created or destroyed in a chemical reaction. Therefore, the mass before and after a chemical reaction remains the same.

Atom

The smallest unit of matter that retains the properties of an element. It is composed of a central nucleus containing protons and neutrons (inside the nucleus), surrounded by electrons (outside the nucleus). An atom has a negative and equal positive charge, resulting in it having no charge ((+1)+(-1)=0). This is because an atom has an equal number of protons and electrons.

Law of Definite Proportions

The suggestion that the number of atoms of the elements in a given compound always exist in the same ratio. EX: multiple samples of the same substance have different amounts of grams of Carbon and Hydrogen, however despite the difference in grams, the mass ratio of Carbon and Hydrogen is always the same. In this case, for all samples the ratio of grams in Carbon and Hydrogen is is 5.33:1.

Law of Multiple Proportions

States that when two elements react to form more than one compound, a fixed mass of one element will react with masses of other elements in a ratio of small, whole numbers. EX: carbon and oxygen form carbon monoxide (CO) and carbon dioxide (CO₂). For a fixed amount of carbon, the mass of oxygen in carbon dioxide will be a whole-number multiple of the mass of oxygen in carbon monoxide (a 1:2 ratio).