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Warm-Up

Warm-Up. What is the difference between atomic mass and atomic number? Can there be an atom with atomic mass that has a decimal? Explain?. Counting Atomic Particles. 5 Main Ways to Represent Atoms Atomic Drawing Using Periodic table Using Specific Isotope Nuclear Symbol Hyphen Notation.

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Warm-Up

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  1. Warm-Up • What is the difference between atomic mass and atomic number? • Can there be an atom with atomic mass that has a decimal? Explain?

  2. Counting Atomic Particles • 5 Main Ways to Represent Atoms • Atomic Drawing • Using Periodic table • Using Specific Isotope • Nuclear Symbol • Hyphen Notation

  3. Counting Subatomic Particles Atom Nucleus Electron Orbits

  4. Periodic Table 74WTungsten 183.85 Atomic Number Atomic Symbol Elemental Name Atomic Mass

  5. Using Specific Isotope 74WTungsten 184 Mass Number

  6. W 184 74 Nuclear Symbol W Mass # Atomic #

  7. Hyphen Notation • Name of Element – mass # • Ex. Tungsten -184 or W-184

  8. Atomic Number • Atomic NumberAtomic #: Number given to the elements according to properties • Number of protons determines the identity of an element • Number of electrons a neutral atom has

  9. Ions • Ion: an atom with a charge due to the loss or gain of electrons. • If a neutral atom loses electrons, it becomes a positive ion because there are more protons than electrons. • If a neutral atom gains electrons, it becomes a negative ion because there are more electrons than protons. • Ex: If S gains 2 electrons, it has __ (+)’s and __ (-)’s for an overall charge of ___. This is represented like this

  10. Mass Number • Mass #: the sum of protons and neutrons • Atomic Mass: average mass of all known isotopes • Isotopes: atoms that are chemically alike but differ in mass; contain different number of neutrons. • Ex: U-235 vs U-238

  11. Isotopes • To find the atomic mass for any element, you must first know 3 things about the element: • The number of stable isotopes of the element • Mass of each isotope • Natural abundance/% of each isotope. • Ex: If H has 3 isotopes, the first with a mass of 1.0078amu & 99.985% abundance, the second with a mass of 2.0141amu & .15% abundance, and the third with a mass of 1.0076amu & .302% abundance, what is the atomic mass of H?

  12. ** Remember, the weight on the periodic table for each element represents the average weight for all of the naturally occurring isotopes of that element

  13. Few Examples

  14. 12 13 14 C C C 6 6 6 Atomic # vs. Atomic Mass • Mass #- protons and neutrons of a specific isotope

  15. Atomic Mass • Atomic Mass- the weighted average of all masses of all isotopes of a specific element • Units- atomic mass unit (amu)

  16. Steps for Calculating Atomic Mass • Convert the % abundance to a decimal. • Multiply the respective decimal by the mass of the isotope. • Add using sig. fig.

  17. Practice

  18. More Practice

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