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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
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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 • 4. Atoms of different elements combine in simple whole number ratios to form compounds • 5. In chemical reactions atoms combine, separate or rearange • 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
Modern Atomic Theory • 2. Atoms of any one element differ in properties from another element • 1. All matter is composed of atoms
The Structure of an Atom Ch 3.2
Subatomic Particles • Electron- • negatively charged, surround the nucleus • Proton- • Positively charged, in nucleus • Neutron- • Neutrally charged, in nucleus
Thompson • Plum Pudding Model • Negative and positive charges spread evenly • Used cathode rays to discover electrons • Found electrons to be negatively charged particles
Rutherford • Used alpha particles to discover the nucleus
Composition of Atomic Nucleus • Positive Charge • Equal in magnitude to the negative chare of an electron(same # of protons and electrons) • Determine atoms identity • Neutral Charge Protons Neutrons
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 • 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 Hyphen Notation Nuclear Symbol
Relative Atomic Masses • Ex:Oxygen-16 • Mass 16/12 of Carbon-12 • 16 amu • Carbon-12 atom • Standard to compare units of atomic mass • Atomic Mass Unit • 1amu = 1/12 mass of Carbon-12
Average Atomic Mass • Calculating AAM • 1.Multiply atomic mass of each isotope by relative abundance • 2. Add the results • Weighted average of atomic masses of naturally occurring isotopes of an element
Relating Mass to Numbers of Atoms • SI unit for amount of substance • Amount of a substance that contains as many particles as are atoms in 12g of carbon-12 • Number of particles in a mole • 6.022 x 1023 Mole Avogadro's Number
Relating Mass to Numbers of Atoms • Mass of 1mole of a pure substance • g/mol Molar Mass Gram/Mole Conversion
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