Atomic structure
- 3. Subatomic Particle Actual Mass Relative Mass Atomic Mass Units Proton 1.673 x 10-24 g 1 1 Neutron 1.675 x 10-24 g 1 1 Electron 9.11 x 10 -28 g 1/1840 Approximately 0 •Atomic Mass Unit (AMU) = is defined as 1/12 the mass of a carbon – 12 atom
- 4. Atomic & Mass Number • Atomic number: • Mass number: • Atomic Number = number of protons in nucleus • Mass number = protons + neutrons
- 5. Number of electrons • For a neutral atom: number of protons = number of electrons • Atomic number: (# of protons) • Number of electrons: • Mass number: (p+ + n0 )
- 6. Isotope Notation • Atomic Number = number of protons in nucleus • Mass number = protons + neutrons • Number of neutrons = Mass number – atomic number • Number of neutrons:
- 7. Examples 1. Neon – 20 – Protons: – Neutrons: – Electrons: – Atomic #: – Mass #: – Isotope Notation: 2. Iron – 56 – Protons: – Neutrons: – Electrons: – Atomic #: – Mass #: – Isotope Notation:
- 8. Isotopes • Definition: – Atoms of the SAME element, but different MASS • What is different between these 3 atoms?
- 9. Atom OR Ion? K – Protons: – Neutrons: – Electrons: – Atomic #: – Mass #: K+1 – Protons: – Neutrons: – Electrons: – Atomic #: – Mass #:
- 10. Atom OR Ion? S – Protons: – Neutrons: – Electrons: – Atomic #: – Mass #: S-2 – Protons: – Neutrons: – Electrons: – Atomic #: – Mass #:
- 12. Radioactive • Low Mass – Elements 1-20 – Stable – n/p ratio = 1 – Unstable – Above or Below • Middle Mass – Elements 21-83 – Stable – n/p ratio = • 1 to 1.5 Unstable – Above or Below •NOTE: All atoms of elements above 83 are radioactive!!!
- 13. Radioactive • Radioactive – Elements 84 and above (all isotopes) – n/p ratio is too large • Conclusions: – Number n0 = number p+ Stable – Atoms above or below this ratio Unstable – More mass Unstable (radioactive)
- 14. Radioactive • Lithium - 8 • Number protons: • Number neutrons: • n/p = • Lead - 214 • Number protons: • Number neutrons: • n/p =
- 15. Radioisotopes • Definition: – a radioactive isotope of an element; produced either naturally or artificially