The Atom Ch 3.1

Foundations of Atomic Theory Law of Conservation of Mass Mass cannot be created or destroyed Law of Definite Proportions Chemical compound always has the same proportions of elements no matter the size Law of Multiple Proportions When elements combine, they do so in the ratio of small whole numbers. The mass of one element combines with a fixed mass of another element 

Dalton’s Atomic Theory 1. Matter is composed of atoms 2. Atoms of a given element are identical in mass, size, and properties 3. Atoms cannot be created or destroyed 4. Atoms of different elements combine in simple whole number ratios to form compounds 5. In chemical reactions atoms combine, separate or rearange

Modern Atomic Theory 1. All matter is composed of atoms 2. Atoms of any one element differ in properties from another element

The Structure of an Atom Ch 3.2

Subatomic Particles Electron- Proton- Neutron- negatively charged, surround the nucleus Proton- Positively charged, in nucleus Neutron- Neutrally charged, in nucleus

Thompson Used cathode rays to discover electrons Found electrons to be negatively charged particles Plum Pudding Model Negative and positive charges spread evenly

Rutherford Used alpha particles to discover the nucleus

Composition of Atomic Nucleus Protons Neutrons Positive Charge Equal in magnitude to the negative chare of an electron(same # of protons and electrons) Determine atoms identity Neutral Charge

Nuclear Forces Hold nuclear particles together Proton- Proton force Neutron-Neutron Force Proton-Neutron Force

Counting Atoms Ch 3.3

Atomic Number The number of protons of each atom in the element Z In order on periodic table

Isotopes Atoms of the same element with different number of neutrons(different mass)

Mass Number Total number of protons and neutrons

Designating Isotopes Hyphen Notation Nuclear Symbol Mass written with a hyphen after the element name Hydrogen-3 1 Proton 1 Electron 2 Neutrons Element mass and atomic # written with the elements symbol Neutrons= Mass-atomic

Practice

Relative Atomic Masses Carbon-12 atom Standard to compare units of atomic mass Atomic Mass Unit 1amu = 1/12 mass of Carbon-12 Ex:Oxygen-16 Mass 16/12 of Carbon-12 16 amu

Average Atomic Mass Weighted average of atomic masses of naturally occurring isotopes of an element Calculating AAM 1.Multiply atomic mass of each isotope by relative abundance 2. Add the results

Relating Mass to Numbers of Atoms Mole Avogadro's Number Number of particles in a mole 6.022 x 1023 SI unit for amount of substance Amount of a substance that contains as many particles as are atoms in 12g of carbon-12

Relating Mass to Numbers of Atoms Molar Mass Gram/Mole Conversion Mass of 1mole of a pure substance g/mol

Practice

Practice

Conversions with Avogadro's Number Avogadro's Number can be used to find The number of atoms in an element The amount of an element in moles

Practice

Practice