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Atoms and Molecules

Atoms and Molecules. Basic units of EVERYTHING!. Atoms. In our model of scale, remember that the BB represented an atom. Hydrogen. Helium. As a class, identify the atoms represented here and label the sub-atomic particles.

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Atoms and Molecules

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  1. Atoms and Molecules • Basic units of EVERYTHING!

  2. Atoms

  3. In our model of scale, remember that the BB represented an atom.

  4. Hydrogen Helium As a class, identify the atoms represented here and label the sub-atomic particles.

  5. What elements are represented here? Use the Periodic Table on the wall to identify these atoms. What does the term “valence shell” mean? Label the valence shell on each of these.

  6. Ions Loss or gain of an electron makes an atom into an ion. Losing an electron makes a positive or negative ion? - + Gaining an electron makes a positive or negative ion? -

  7. Isotopes Atoms that gain or lose a neutron become isotopes. Radioactive isotopes are used in medicine for imaging (such as PET scanners).

  8. Why is this important? • Each element has distinct properties: color, melting point, reactivity, etc. • The basic atomic structure of each element determines that element’s properties. Change the structure, and you have an entirely different element.

  9. Atoms bond together • Molecules are made up of atoms bonded together. • The structure of an individual atom determines: • Whether the atom can form bonds. • How many other atoms it can bond to.

  10. In our model of scale, remember that the marble represented a small molecule, such as glucose.

  11. How many atoms can each of these atoms bond with? How do we know?

  12. Fill in the blank column with number of covalent bonds formed by each atom.

  13. Ionic Bonding

  14. Ionic substances tend to form crystaline lattices rather than distinct molecules.

  15. Covalent Bonding Co = together valent = valence shells The hydrogen atom. How many bonds can it form?

  16. Covalent bonding A hydrogen molecule. How many hydrogen atoms are involved? Can there be more? Why or why not?

  17. Covalent Bonding

  18. Polar bonding between atoms produces a polar molecule, which has areas with slightly positive or slightly negative charges.

  19. Why is polarity so important? Salt dissolves in water. Oil does not. Why? What will oil dissolve in? Why?

  20. Molecules bond together Weak attractive forces between molecules are called hydrogen bonds.

  21. Here, sugar (a polar substance) is in solution with water (also polar). Mark where the hydrogen bonds will form.

  22. Water is: Cohesive Adhesive A “universal solvent” Water also has: A high specific heat A high heat of vaporization Properties of Water

  23. pH is a ratio between H+ and OH- ions in solution.

  24. Recap • What is the difference between atoms and molecules? • What is the difference between ionic bonding and polar covalent bonding? • How is polarity related to pH?

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