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Put HW into the bin Quiz on Chem vocabulary Review HW-notes!. Chemistry Review. You need to remember some basic things. The Atom. Smallest possible unit that maintains properties of the element Made of: Protons – positively charged particles, define the element , atomic number

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Put HW into the bin

  • Quiz on Chem vocabulary
  • Review HW-notes!
chemistry review

Chemistry Review

You need to remember some basic things

the atom
The Atom
  • Smallest possible unit that maintains properties of the element
  • Made of:
    • Protons – positively charged particles, define the element, atomic number
    • Neutrons- neutral particles, isotopes
      • Together form the atomic nucleus
    • Electrons- negatively charged particles, Bonding
      • Fly around the nucleus
  • Each element has a unique number of protons (atomic number)
electron orbitals shells
Electron Orbitals/Shells
  • Electrons are found in characteristic areas around the nucleus, called an orbital
    • Each one represents a different energy level
  • Simplifying things, orbitals are grouped into “shells”
electron shells
Electron Shells
  • The innermost shell of orbitals is filled first
  • Electrons are distributed to each orbital in a shell before filling each orbital
  • The outermost shell is called the valence shell
using the periodic table
Using the Periodic Table
  • Ignore the metals
  • The row tells you the # of shells the atom should have
  • The column tells you the # of valence electrons a neutral atom should have in its valence shell
  • Aka charged atoms
  • + ions occur when there are more protons than electrons
  • - ions occur when there are more electrons than protons
  • Atoms can gain and lose electrons
lewis structures
Lewis Structures
  • Only show the outer most shell electrons or the VALENCE electrons

(only showing the valence electrons)

draw lewis model
Draw Lewis model:
  • Oxygen
  • Carbon
  • Hydrogen
filling valence shells
Filling Valence Shells
  • Generally chemical reactions occur that fill valence electron shells
  • Either by gaining/losing electrons


  • By sharing electrons with other atoms
6a covalent bond
6a. Covalent Bond
  • Sharing of electrons between two atoms
  • A single bond consists of 2 shared electrons, which occupy the valence shell of both atoms
    • Double bond = 4 electrons
    • Triple bond = 6 electrons
guidelines of bonding
Guidelines of Bonding
  • Atoms almost always will end up with 8 electrons in their valence shell (may be lone pairs or shared electrons)
  • So an atom that normally has 6 valence electrons needs to get 2 more from bonding
The column can be used to figure out how many bonds an atom will normally form! This is DIFFERENT than the valence number!

4 3 2 1 0

lewis structures for molecules
Lewis Structures for molecules
  • A line represents 2 electrons, usually shared in a covalent bond
  • Dots represent electrons that are held by only one atom (lone pairs)
  • Only valence electrons are shown
  • Each atom should have a total of 8 electrons (except H and He which hold 2)
6b polar vs non polar covalent bonds
6b.Polar vs. Non-Polar Covalent Bonds



  • Electrons shared equally
  • Both atoms have similar electronegativity (affinity for electrons)
  • Neither atom ends up with any charge
  • Electrons not shared equally
  • 1 atom is more electronegative (typically O, F, N, & Cl )
  • Electronegative atom ends up with a partial – charge since they often “hog” the electron
  • Other atom ends up with a partial + charge as they have the electron less.
All atoms attract electrons to themselves differently. This is measured by a number called an atom’s ELECTRONEGATIVITY (EN). The HIGHER this number is, the more strongly the atom pulls electrons toward itself.
10 ion formation
10. Ion Formation
  • Some atoms more easily give up e- (1st and 2nd columns) to get a full valence shell
  • They commonly form bonds with atoms in the 6th & 7th column (respectively) since they need 1 or 2 e-
  • This is 1 way to form ions

There other 2 ways to turn an atom into an ion.

    • Light, e.g. photoelectric effect: where the energy of the incident photon kicks the electron out of its orbit. EX: PHOTOSYNTHESIS
    • Heat: where the kinetic energy of atom and electron vibrations is so large that the electron vibrates away from the atom and does not return.
6c ionic bonding
6c. Ionic Bonding
  • Opposites attract!
  • Significantly weaker than a covalent bond
  • Can also occur between ionic molecules
11 intermolecular bonds
11. Intermolecular Bonds
  • Between 2 different molecules (think interstate highway is between 2 different states)
  • I.e. hydrogen bonds in water
  • Much weaker than intramolecular bonds
  • aka intermolecular forces, attractions
hydrogen bonds
Hydrogen Bonds
  • Weak attraction between the partial charges of polar covalently bonded molecules
  • In water, between O and H

Means partial

IV. Some Final Key Points…

A. Molecules are 3-dimensional and have a variety of shapes.

  • 1. The shape of molecules is very important because the ability of molecules to bind with one another is the basis of most functions in our bodies!