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CHEMISTRY

CHEMISTRY. Basic Concepts Types of Reactions. A world of atoms. 2,400 years ago, Democritus proposed That the world is made of atoms. The word atom is Greek for “not breakable.” ( learn more )

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CHEMISTRY

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  1. CHEMISTRY Basic Concepts Types of Reactions

  2. A world of atoms 2,400 years ago, Democritus proposed That the world is made of atoms. The word atom is Greek for “not breakable.” (learn more) In the early 1800’s John Dalton revived atomic theory. He argued that chemical reactions were the rearrangement of atoms. Democritusfrom Essays on Physiognomy.By John Caspar Lavater, trans. Henry Hunter, London, 1789 [vol I]book containing 4 engraved illustrations by BlakeAcquired at unknown date National Gallery of Victoria

  3. Today, we believe atoms consist of a small, massive, positively charged nucleus orbited by light, negatively charged electrons. Modern Atoms The negative electrons are attracted to the positive nucleus and orbit around it. It is surprising that the part of the atom that accounts for all its mass (the nucleus) accounts for almost none of its volume.

  4. The Nucleus The nucleus (plural nuclei) is made of two different particles: the positively charged proton and the neutral neutron. Positively charged protons repel one another. A new force (the strong force) is needed to hold them and the neutrons together in the nucleus (learn more).

  5. Electron Energy Levels The electrons orbiting around the nucleus do so in discrete orbits. Each orbit has a specific energy level. The farther out the orbit, the higher its energy.

  6. Ions • Atoms are neutral: they have an equal number of positive protons and negative electrons. • Atoms can become charged either by gaining or losing an electron. • Ions are indicated with a (+) or (-) sign

  7. The Periodic Table All known elements are listed in the Periodic Table. Each element in a column on the periodic table has a similar arrangement of outer electrons. This means they take part in similar chemical reactions. online periodic table

  8. Isotopes The periodic table on the previous slide lists the atomic number and atomic mass of each element. Atomic Number = number of protons Atomic Mass = # of protons + # of neutrons • Notice that the atomic mass is not always a whole number. It’s a weighted average. • Some atoms of an element have different numbers of neutrons. • These atoms have different atomic masses and are called isotopes.

  9. Molecules Press down arrow to view animation Sometimes when atoms bump into one another, their outer electrons interact – hooking the atoms together and forming a molecule. (learn more) Press up arrow to reset animation H + H  H2

  10. Press down arrow to view animation Press up arrow to reset animation O + H + H  H2O

  11. Types of Chemical Reactions(all of these happen in space!!) In the following slides, press the down arrow to view the animation and the up arrow to reset the animation Combination Decomposition Ionization Radiative Recombination Single Replacement Negative Ion Reaction Charge Transfer Double Replacement

  12. Combination Press down arrow to view animation Press up arrow to reset animation C + O  CO

  13. Decomposition Press up arrow to reset animation Press down arrow to view animation SiO  Si + O

  14. (+) Ionization (+) Press up arrow to reset animation Press down arrow to view animation Na  Na+ + e-

  15. Radiative Recombination Press up arrow to reset animation Press down arrow to view animation H+ + e- H

  16. Single Replacement Press up arrow to reset animation Press down arrow to view animation HCl + Na  NaCl + H

  17. Negative Ion Reaction Press up arrow to reset animation Press down arrow to view animation Cl- + Cl  Cl2 + e- Note: Cl2 has not been detected in space

  18. Charge Transfer (+) Press down arrow to view animation Press up arrow to reset animation SO + H+  SO+ + H

  19. Double Replacement Press up arrow to reset animation Press down arrow to view animation CH + NO  CO + NH

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