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Published byJayson Carpenter Modified over 9 years ago
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Review of Atomic Model
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Key Words subatomic particle energy levels atomic mass protonisotope electronneutronion atomic mass unit (u)atomic number
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Elements are pure substances containing one type of atom – found on the Periodic Table. The atom is the smallest part that retains all the properties of that element. protons (p + )neutrons (n o )electrons (e - ) Charge Mass Location +1.6 x 10 -19 C0-1.6 x 10 -19 C 1.67 x 10 -24 g 9.11 x 10 -28 g Nucleus Orbit clouds
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The atomic number (Z) is the number of protons in the nucleus of an atom - identifies an element. The atomic mass (A) is the number of protons plus the number of neutrons.
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H : the hydrogen atom H + : a positively charged hydrogen ion H - : negatively charged hydrogen ion Ion: an atom that has gained or lost electrons. Results in a negative or positive charge equal to the electrons transferred. Neutral: an atom with the same number of protons and electrons – cancelled charges.
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Deuterium Atomic Mass = 2 Atomic Number = 1 Hydrogen Atomic Mass = 1 Atomic Number = 1 Isotopes: Atoms with the but a different number of neutrons. Atomic mass is actually an average of isotopes of an element based on relative abundance in nature. same number of protons
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Mass spectrometer determines the mass of individual atoms or isotopes. Sends atoms through a magnetic field which bends their paths. The heavier the atom – the less it bends.
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Potassium isotopes: 1. 19 protons and 20 neutrons - mass number of 39 (potassium-39 39 K) 2. 19 protons and 21 neutrons - mass number of 40 (potassium-40 40 K) 3. 19 protons and 22 neutrons - mass number of 41 (potassium-41 41 K)
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Magnesium exists as three isotopes in the world: 78.99% is 24 Mg (23.985 μ) 10.00% is 25 Mg (24.986 μ) 11.01% is 26 Mg (25.982 μ) (0.7899)(23.985 μ) = 18.95 μ (0.1000)(24.986 μ) = 2.499 μ (0.1101)(25.982 μ) = 2.861 μ = 24.31 μ + Calculate the average atomic mass of magnesium:
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helium 5 He 6 He The nucleus of some isotopes are unstable and break apart over time - radioactivity.
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Radioisotopes - unstable nuclei releasing energy and/or particles. Release of energy is called radioactive decay. Atom may be converted into another isotope or a completely different element. Half-life - amount of time it takes for half the radioisotope to be converted into another particle.
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Many different types of decay: alpha decay, beta decay, gamma decay
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Isotopes - differ in mass because they have different numbers of neutrons. Relative / percent abundance is the fraction of each isotope found in an average sample of the element.
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