ATOMIC THEORIES AND VALENCE ELECTRONS
ATOMIC THEORIES• Dalton thought that atoms were like
smooth, hard balls that could not be broken into smaller pieces.
ATOMIC THEORIES• Thomson suggested that atoms had
negatively charged electrons embedded in a positive sphere.
ATOMIC THEORIESBohr Model- Everything moved around nucleus
Rutherford-Atom mostly empty space
ATOMIC THEORIESRutherford was surprised that a few particles were deflected strongly. This led him to propose an atomic model with a positively charged nucleus.
ATOMIC THEORIES• Through the first part of the twentieth
century, atomic models continued to change. Cloud Model-
1920’sElectrons move rapidly every which way
WHAT DOES IT MEAN TO BE REACTIVE?• We will be describing elements according to
their reactivity. • Elements that are reactive bond easily with
other elements to make compounds.• Some elements are only found in nature bonded
with other elements. • What makes an element reactive?
– An incomplete valence electron level.– All atoms (except hydrogen) want to have 8 electrons
in their very outermost energy level (This is called the rule of octet.)
– Atoms bond until this level is complete. Atoms with few valence electrons lose them during bonding. Atoms with 6, 7, or 8 valence electrons gain electrons during bonding.
VALENCE ELECTRONS• Number of E- on the outer shell (the
outside ring of the onion) of atom, which determines reactivity of the atom
• Noble gases: 8 valence e- except He(helium) has 2= stability– Elemental square info (stats)
• Stability- Is not actively seeking any other elements (nope is not dating, is okay being alone because it has everything it needs)
• Example: Oxygen has 6 valence e- = not stable – Actively seeking other elements (yep, dating
but not exclusive, has been seen with hydrogen and
calcium)
VALENCE ELECTRONS• The number of valence electrons in an
atom of an element determines many properties of that element, including the ways in which the atom can bond with other atoms.
• Atoms usually react in a way that • makes them more stable– Scenario A: The number of valence e-
increases to 8– Scenario B: The atom gives up loosely held
valence e- (usually 1 or 2 valence e-)
LEWIS DOT STRUCTURE• Shows the valence electron dot
structures of atoms and bonding that occurs among atoms
Yes ,this is Gilbert Lewis
WHAT DOES THAT MEAN TO ME?• With a Lewis dot structure, you can show
the valence e- of the atom • AND…How bonding occurs among
different atoms!
PRACTICE LEWIS DOT STRUCTURES• Li• B• Cl• K
• Al• S• Ca• Kr
BONDING• Chemical Bond- the force of attraction
that holds 2 atoms together as a result of the rearrangement of e- between them
• The number of valence e- determines whether or not atoms will bond together
Would be the bonding enforcers of the atom world
BONDING