Chapter #2 Lecture Part 2
- 1. Atomic Mass Atomic and molecular masses can be measured with great accuracy with a mass spectrometer.
- 2. Average Atomic Mass or Atomic Weight Because in the real world we use large amounts of atoms and molecules, we use average masses in calculations. Average mass is calculated from the isotopes of an element weighted by their relative abundances.
- 3. Periodic Table A systematic catalog of elements.
- 4. Periodicity When one looks at the chemical properties of elements, one notices a repeating pattern of reactivities.
- 5. Periodic Table The rows on the periodic chart are periods.
- 6. Groups
- 7. Periodic Table Nonmetals are on the right side of the periodic table (with the exception of H).
- 8. Periodic Table Metalloids border the stair-step line (with the exception of Al and Po).
- 9. Periodic Table Metals are on the left side of the chart.
- 10. Chemical Formulas The subscript to the right of the symbol of an element tells the number of atoms of that element in one molecule of the compound.
- 11. Molecular Compounds Molecular compounds are composed of molecules and almost always contain only nonmetals.
- 12. Diatomic Molecules These seven elements occur naturally as molecules containing two atoms.
- 13. Types of Formulas Empirical formulas give the lowest whole-number ratio of atoms of each element in a compound. Molecular formulas give the exact number of atoms of each element in a compound.
- 14. Types of Formulas Structural formulas show the order in which atoms are bonded. Perspective drawings also show the three-dimensional array of atoms in a compound.
- 15. Ions When atoms lose or gain electrons, they become ions. Cations are positive and are formed by elements on the left side of the periodic chart. Anions are negative and are formed by elements on the right side of the periodic chart.
- 16. Ionic Bonds Ionic compounds (such as NaCl) are generally formed between metals and nonmetals.
Editor's Notes
- #2: Figure 2.13