chapter 7 lesson 2 isotopes and radioactivity. what’s the difference between the two atoms in...

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  • Chapter 7 Lesson 2Isotopes and Radioactivity

  • Whats the difference between the two atoms in Figure 12?

    Left

  • Isotopes Different Numbers of NeutronsWhats the difference between the two atoms in Figure 12?

    O-17 has one extra neutronThese two atoms are called Isotopes

  • How Many Neutrons?Isotopes with more neutrons are heavier than isotopes with fewer neutrons.Lets calculate the number of neutrons in a Carbon-14 atom:

  • How many neutrons?How many neutrons are in Carbon-12 atoms?

    How many neutrons are in Carbon-13 atoms?Left

  • How many neutrons?How many neutrons are in Carbon-12 atoms?12 6 = 6 neutronsHow many neutrons are in Carbon-13 atoms?13 6 = 7 neutrons

  • What determines properties?Chemical properties are determined by the number of valence electrons an atom has.Valence electrons determine what type of bond an element will form.Do isotopes have similar chemical properties??

  • What determines properties?Chemical properties are determined by the number of valence electrons an atom has.Valence electrons determine what type of bond an element will form.Do isotopes have similar chemical properties??Yes they do, because they have the same number of electrons.

  • What is radioactive decay?The three isotopes of Carbon have similar properties, but C-14 is radioactive.

  • What is radioactive decay? When radioactive decay occurs, an unstable atomic nucleus changes into another nucleus by releasing one or more particles and energy.

    Stability increases and a different element is formed. (See Figure 15 on page 303)

  • Uses of Radioactive DecayLook on page 304 at the bottom.List 3 ways that we have found to use radioactive decayLeft

  • Uses of Radioactive DecayLook on page 304 at the bottom.List 3 ways that we have found to use radioactive decay:Medical imagingDetection of cancer cellsKilling of cancer cellsPreservation of food

  • Radioactive Elements and the Periodic TableRadioactive elements = elements that have only radioactive isotopesRadioactive Elements are HEAVY so they are found near the bottom of the periodic table (See figure 18 below)

  • Half-lifeIsotopes decay at very different ratesHalf-life= the time it takes for half of the original sample to decayUranium-235 has a half life of 713 million years!How many grams would be left after another 713 million years?

  • Half-lifeErbium has many isotopes:1. How many seconds is the half-life for Er-147?2. How much time would it take for a 100g sample of Er-145 to decay to a 25g sample?3. How much time would it take for a 200g sample of Er-169 to decay to a 100g sample? Left

    Half-Lives of ErbiumIsotopeHalf-LifeEr-1450.9 sEr-1472.5 sEr-1543.73 minEr-15619.5 minEr-1582.29 hEr-1699.40 days

  • Half-lifeErbium has many isotopes:1. How many seconds is the half-life for Er-147? 2.5 s2. How much time would it take for a 100g sample of Er-145 to decay to a 25g sample? (0.9 +0.9 = 1.8 s)3. How much time would it take for a 200g sample of Er-169 to decay to a 100g sample? 9.40 days

    Half-Lives of ErbiumIsotopeHalf-LifeEr-1450.9 sEr-1472.5 sEr-1543.73 minEr-15619.5 minEr-1582.29 hEr-1699.40 days

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