CHAPTER 3!ATOMS AND MOLES

By: Andres Sanchez

Law Of Definite Proportions Law of definite proportions states that two

samples of a give compound are made of the same elements in exactly the same proportions by mass regardless of the sizes or sources of the samples

States that every molecule of ethylene glycol is made of the same number and types of atoms

Example: 51.56% oxygen, 39.70% carbon, and 9.74%

hydrogen

Law Of Conservation Of Mass Law of conservation of mass states

that the mass of the reactants in a reaction equals the mass of the products

Example: Sulfur atom + Oxygen Molecule = Sulfur

dioxide molecule

Law Of Multiple Proportions Law of multiple proportions is if two

or more different compounds are composed of the same elements, the ratio of the masses of the second element is always a ratio of small whole numbers.

Dalton’s Theory Five Principles

1. “All matter is composed of extremely small particles called atoms, which cannot be subdivided, created, or destroyed.”

2. “Atoms of a given element are identical in their physical and chemical properties.”

3. “Atoms of different elements differ in their physical and chemical properties”

4. “Atoms of different elements combine in simple, whole number ratios to form compounds”

5. “In chemical reactions, atoms are combined, separated, or rearranged but never created, destroyed, or changed.”

Subatomic Particles

Electrons- Particles that have mass and a negative charge

Protons- has exactly equal in magnitude but opposite in sign to charge of an electron

(Equal but opposite charges) Neutron- neutral particles which are part of all

atomic nuclei. Atomic Number- The number of protons that an

atom has Mass Number- the total number of particles of the

nucleus mass number – atomic number = Number of

Neutrons

Extranesss…..

Orbitals- regions around a nucleus that make a specific energy level

Hund’s Rule- states that orbitals of the same n and l quantum numbers are each occupied by one electron before any pairing occurs