1. Chapter 3 Atomic Structure

2. The Structure Of the Atom Particle masschargelocation Proton1 AMU +1in nucleus Neutron 1 AMU 0in nucleus Electron 0 AMU -1 outside nucleus Atomic number – number of protons in the nucleus, It determines which element an atom is

3. A neutral atom has the same number of protons as electrons Example: atomic # 12 – magnesium has 12 protons and 12 electrons An atom can gain or lose electrons to become an ion

4. Ions have a charge and are very different than the atoms that they used to be Na is a very reactive metal. http://www5.wittenberg.edu/academics/che m/fac_staff/dmcdowell/alkalishow.html http://www5.wittenberg.edu/academics/che m/fac_staff/dmcdowell/alkalishow.html http://www5.wittenberg.edu/academics/che m/fac_staff/dmcdowell/alkalishow.html Na+ ion is part of table salt and is necessary for life.

5. Isotopes Atoms of an element all have the same number of protons and electrons; however, they can have different number of neutrons. Isotopes – atoms of the same element that differ in their number of neutrons. Isotopes of an element have the same chemical properties (differ only in mass).

6. Isotopes of Hydrogen

7. Isotopes of Carbon

9. Isotopic Notation http://preparatorychemistry.com/Bishop_Is otope_Notation.htm http://preparatorychemistry.com/Bishop_Is otope_Notation.htm # of neutrons = mass # - # of protons 1 AMU = exactly 1/12 the mass of one atom of C-12 The mass of an element given on the chart is an average of the isotopes of that element found in nature.

10. Some isotopes are stable and some are not. If an atom has the wrong number of neutrons it will be unstable (see page 113) Also, if an atom has too many protons (more than 83) it will be unstable. Unstable atoms are radioactive and break down (nuclear decay) They eventually change to a stable element

11. Stability of Isotopes

12. Half life – the time it takes for one half of a sample of a radioactive element to change. If you start with 4 grams of uranium, after one half-life you will have only 2 grams of uranium. The rest will be changed to another element. If you start with 4 grams of uranium, how much will be left after 4 half lives?

13. Types of Radioactive Decay NameIdentityCharge Penetration Alpha particle He nuclei+2 stopped by paper Beta particle electron-1 stopped by clothing Gamma ray, high energy light 0 thick lead used

14. Nuclear Decay of Uranium Emitting alpha and gamma particles Emitting alpha and gamma particles

15. Decay of I-131 emitting beta particle emitting beta particle

16. Decay of Rb-81 Electron capture

17. Assignment: page 122 &123 questions 3-13, 15-21