1 / 18

Atoms

Atoms. -Basics on atomic structure -Isotopes -Isotopic Mass & Relative Atomic Mass. Revision from Year 11. The Bohr model of the atom. It’s not perfect, but it is a simple model. Mass and charge.

becca
Download Presentation

Atoms

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Atoms -Basics on atomic structure -Isotopes -Isotopic Mass & Relative Atomic Mass

  2. Revision from Year 11 • The Bohr model of the atom. • It’s not perfect, but it is a simple model.

  3. Mass and charge • With your partner, try to describe the distribution of mass in an atom (i.e where is it and why?) • Do the same for charge, where is the charge distributed within an atom? • A diagram may help.

  4. The Atomic number. • Each element has a unique atomic number. This number tells us two things: • How many protons the atom has • How many electrons the atom has. Why are these numbers the same?

  5. Atomic Mass. • Try not to confuse the atomic MASS and the atomic NUMBER. • The Atomic Mass tells us how much stuff is in the atom. How many PROTONS and NEUTRONS it has. • Why might we ignore electrons when we talk about atomic mass?

  6. Atomic number & atomic mass • Atomic Mass • Found in the periodic table • Tells us the of protons AND neutrons in the nucleus • A larger number than the atomic number. • Atomic number • Found in the periodic table • Table arranged by increasing atomic number • Tells us the number of protons in the nucleus.

  7. We’re pretty lazy • We have a short way of writing the atomic number and the mass number for an element: • Which number is atomic number, which is the mass number?

  8. Isotopes. • Isotopes are elements of the same type but with different mass.

  9. Chlorine has two stable isotopes. • How many protons and neutrons does each have? Try the others. 35Cl 131I12C 37Cl 127I13C

  10. Carbon 12. It’s important. • 12C is used as a standard for the measurement of relative mass. • Atomic masses are measured using a unit called unified atomic mass unit. • This is a tiny number- 1 u is 1.66 x 10-27 • Mass of carbon atom- 12 u • So one twelfth of an atom of carbon is 1 u

  11. Relative isotopic mass • The Relative Isotopic Mass is the mass of an atom of an isotope compared to one twelfth of the mass of an atom of Carbon-12.

  12. Relative isotopic mass • The Relative Isotopic Mass is the mass of an atom of an isotope compared to one twelfth of the mass of an atom of Carbon-12. • The Relative Isotopic Mass is the mass of an atom of an isotope compared to one twelfth of the mass of an atom of Carbon-12.

  13. Relative atomic mass. Ar • In a lump of carbon we have 12C and 13C. • These weigh a different amount. • We use a ‘weighted mean mass’ to account for this. • This depends on: • The percentage abundance of the isotope • The relative mass of the isotope.

  14. Ar Definition • The relative atomic mass is the weighted mean mass of an atom of an element compared to one-twelfth of the mass of an atom of carbon-12

  15. Ar Definition • The relative atomic mass is the weighted mean mass of an atom of an element compared to one-twelfth of the mass of an atom of carbon-12 • The relative atomic mass is the weighted mean mass of an atom of an element compared to one-twelfth of the mass of an atom of carbon-12

  16. Ar • For example: • Boron contains 19.77% 10B and 80.23% 11B • Ar(B)= (19.77/100 x 10) + (80.23/100 x 11) = 1.977 + 8.8253 = 10.8023 u

More Related