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    • Lab - Measurement >
      • Measurement Lesson 1
      • Measurement Lesson 2 Scientific Measurements
      • Measurement Lesson 3 Significant Figures
      • Measurement Lesson 4 Units
      • Measurement Lesson 5 Skills
    • 1. Matter & Energy >
      • Matter Lesson 1 Types of Matter
      • Matter Lesson 2 Mixtures and Separation
      • Matter Lesson 3 Properties and Changes
      • Matter Lesson 4 Phases of Matter
      • Energy Lesson 5 Heating and Cooling Curves
      • Energy Lesson 6 Heat Definitions
      • Energy Lesson 7 Calculating Heat
    • 2. Gas laws >
      • Gas Laws Lesson 1 Gas Laws
      • Gas Laws Lesson 2 Combined Gas Law
    • 3. Atomic Theory & Periodic Table >
      • Lesson 1 Atomic Theory
      • Lesson 2 Subatomic Particles
      • Lesson 3 Foundations of PT
      • Lesson 4 Types of Elements
      • Lesson 5 Electrons
      • Lesson 6 Atoms vs Ions
      • Lesson 7 Oxidation Numbers
      • Lesson 8 Electron Dot Diagrams
      • Lesson 9 Isotopes
      • Lesson 10 Periodic Trends
    • 4. Bonding >
      • Bonding Lesson 1 Basics
      • Bonding Lesson 2 Ionic Bonds
      • Bonding Lesson 2b Stock System
      • Bonding Lesson 3 Covalent Bonds
      • Bonding Lesson 3b Naming Covalent Bonds
      • Bonding Lesson 3c Multiple Bonds and Bond Strength
      • Bonding Lesson 4 Metallic Bonds
      • Bonding Lesson 5 Symmetry
      • Bonding Lesson 6 IMF
    • 5. Nuclear >
      • Nuclear Lesson 1 Transmutation
      • Nuclear Lesson 2 Radioisotope Uses
      • Nuclear Lesson 3 Radiation Penetration
      • Nuclear Lesson 4 Artificial Transmutation
      • Nuclear Lesson 5 Half Life
    • 6. Formulas and Equations >
      • Formulas & Equations Lesson 1 Types of Formulas
      • Formulas & Equations Lesson 2 Types of Reactions
      • Formulas & Equations Lesson 3 Balancing Equations
    • Semester 2 >
      • 10. Math & Moles >
        • Math Lesson 1 Mass
        • Math Lesson 2 Percent Composition
        • Math Lesson 3 Avogadro
        • Math Lesson 4 Molecular Formula from Empirical
        • Math Lesson 5 Mole Ratios
      • 11. Solutions >
        • Solutions Lesson 1 Solutions
        • Solutions Lesson 2 Solubility
        • Solutions Lesson 3 Concentration
        • Solutions Lesson 4 Colligative Properties
      • 12. Acids & Bases >
        • Acids and Bases Lesson 1 Properties
        • Acids and Bases Lesson 2 Naming
        • Acids and Bases Lesson 3 Reactions
        • Acids and Bases Lesson 4 pH Scale
        • Acids and Bases Lesson 5 Indicators
      • 13. Kinetics & Equilibrium >
        • Kinetics & Equilibrium Lesson 1 Collision Theory and Factors
        • Kinetics & Equilibrium Lesson 2 PE Diagrams
        • Kinetics & Equilibrium Lesson 3 Equilibrium
        • Kinetics & Equilibrium Lesson 4 LeChateliers Principle
        • Kinetics & Equilibrium Lesson 5 Entropy and Enthalpy
      • 14. Oxidation Reduction >
        • RedOx Lesson 2 RedOx Reactions
        • RedOx Lesson 3 Half Reactions
        • RedOx Lesson 4 Spontaneous Reactions
        • RedOx Lesson 5 Electrochemical Cells
      • 15. Organic >
        • Organic Lesson 1 Intoduction
        • Organic Lesson 2 Hydrocarbons
        • Organic Lesson 3 Functional Groups
        • Organic Lesson 4 Reactions
  • Review Material
    • Textbook Unit Review Sheets
  • NYS Chemistry Curriculum

Isotopes

Remember isotopes of an element have the same number of protons (that can NEVER change) but a different number of neutrons resulting in a different mass.
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Calculating Averages
Class Average
your grade is 85% test/quiz
                            15% hw/lab/part
If your test average is 75 and your hw average is 100, what will your class average be?
Can they be treated equally? 
Is it 87.5 or 78.75? 

Calculating Average Atomic Mass
Step 1: convert % to decimal (divide by 100)
Step 2: multiply mass by decimal
Step 3: repeat for ALL isotopes and add


Class Average
your grade is 85% test/quiz
                            15% hw/lab/part
If your test average is 75 and your hw average is 100, what will your class average be?





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What is the avearge atomic mass for lithium?
Naturally occurring boron is composed of two isotopes. The percent abundance and
the mass of each isotope are listed below.
• 19.9% of the boron atoms have a mass of 10.013 atomic mass units.
• 80.1% of the boron atoms have a mass of 11.009 atomic mass units.
Is the atomic mass going to be closer to 10 or 11?


What is the average atomic mass for boron?



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Mg-26 1.75 %         Mg-24  98.25% 
What is the average atomic mass?



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What is the average atomic mass for strontium?
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