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Chemistry

A walk down memory lane… Or at least it should be. Chemistry. If you can cook, you can do chemistry!. The ingredients = reactants The cake/ cookies = produc t You only get out what you put in ( Conservation of mass ) Your products do not have the same properties as the reactants

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Chemistry

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  1. A walk down memory lane… Or at least it should be Chemistry

  2. If you can cook, you can do chemistry! • The ingredients = reactants • The cake/ cookies = product • You only get out what you put in (Conservation of mass) • Your products do not have the same properties as the reactants • Does a cake taste the same as raw eggs, flour, etc?

  3. Atoms – The smallest unit of matter that cannot be broken down by chemical means *All matter consists of atoms Nucleus • Protons (+) • Neutrons (0) Electron Cloud • Electrons (-) * Nuclei can only be changed by fission or fusion! *

  4. Electron Clouds S orbital • Areas of probability • Electrons do not really travel in orbits like planets • Bohr Model • Electrons are in clouds • The farther from the nucleus, the easier an e- is lost p orbitals

  5. Elements: a pure substance made of only one kind of atom Atomic Number • Each element: • Has a different number of protons • Has a symbol (one or two letters) • Organized on the periodic table 36 Kr Krypton 83.80 Symbol Atomic Weight

  6. How do we figure out the number of protons, neutrons, and electrons? • Atomic Number = the number of protons which = the number of electrons • Atomic Weight = the total mass of the atom. Comes from the combination of protons and neutrons 36 Kr Krypton 83.80 Protons = atomic number = 36 Electrons = atomic number = 36 Neutrons = atomic weight – atomic number = 84-36= 48

  7. Isotopes: atoms of the same element that have the same number of protons, but a different number of neutrons • Some isotopes are stable • Some break apart and release energy (fission) This is the reason why atomic weights are NOT whole numbers!

  8. Organized by properties: Periodicity • Period – horizontal rows • Group – Vertical column • Valence electrons – outermost e-, involved in bonding, same as the group number for the main block elements

  9. Patterns in the Periodic Table • Diameter decreases as you move along the row from left to right • Diameter increases as you move down the column • Each column reacts similarly, because they have the same number of valence electrons • Metals are on the left and nonmetals on the right

  10. Lets put some atoms together! • Compound – two or more atoms joined together • Molecule – two or more atoms share electrons

  11. Types of Chemical Bonds • Ionic • Electrons are transferred • Makes ions when dissolved • Forms between a metal and a nonmetal • Covalent • Electrons are shared • Forms between 2 nonmetals • Polar: e- are NOT equally shared • Non-polar: e- ARE equally shared * Don’t forget: “Like dissolves like”

  12. Metallic Bonds • Electrons move from one atom to the next • Forms between 2 metals

  13. Hydrogen Bond • Between 2 polar MOLECULES • Weak bond • Positive and negative charges attract much like opposite poles of a magnet Partially Negative Partially Positive *This allows for adhesion, cohesion, and capillary action in water*

  14. Balancing Chemical Formulas • Step 1: determine the charge of the ion each element will form • Step 2: Write the metal first, the nonmetal second • Step 3: the charge of one atom is the subscript of the other Mg2+ Cl- MgCl2

  15. Polyatomic Ions • “ion with many atoms” • The atoms in the polyatomic react as if they are one atom – they do not rearrange • Written with parentheses around them if more than one polyatomic is in the compound • Mg(OH)2

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