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