bond. chemical bond
DESCRIPTION
Bond. Chemical Bond. ELECTRONEGATIVITY The tendency of an atom to attract electrons to itself when it is bonded to another atom. Check out Figure 5-20 on page 151. Where are electronegativities the greatest? The least?. OCTET. The eight outer electrons in an atom. FACT: - PowerPoint PPT PresentationTRANSCRIPT
Bond.Chemical Bond.
ELECTRONEGATIVITY
The tendency of an atom to attract electrons to
itself when it is bonded to another atom
Check out Figure 5-20
on page 151•Where are electronegativities the greatest?
•The least?
The eight outer electrons in an
atom
OCTET
FACT:Atoms with full outer energy levels are very stable (less reactive)
If an atom has 8 electrons in its outer
energy level, it is unreactive (save He)
OCTET RULE
Pretend we had a sub-energy level with 12
electrons. When would it be most
stable?(The egg carton example)
FACT #2:Atoms with filled,
half filled, or empty sub-energy levels are slightly more stable
Now…how do we make ENERGY LEVELS more
stable?
Ways to make full outer energy levels:
•Add electrons to a partially filled outer energy level•Lose all electrons in the outer energy level•Share electrons with another atom
Periodic Trends
ATOMIC RADIUS
The distance from the center of the nucleus
to the outermost energy level
The atomic radius INCREASES
within a group
(just adding energy levels)
The atomic radius DECREASES
within a period
(more positive charge pulling e-)
SHIELDING EFFECT
The positive pull is less because the distance between nucleus and electrons is greater
IONIZATION ENERGY
the energy required to remove an electron
from an atom
The ionization energy
INCREASES across a period
(more p+ have more pull on e-)
The ionization energy DECREASES as you
go down a group
(shielding effect)
ELECTRON AFFINITY
how much an atom desires another
electron
The electron affinity DECREASES as you
go down a group
(shielding effect)
The electron affinity INCREASES across a period
(except for the noble gases)
(more p+ have more pull on e-)
BOND STRENGTHthe energy needed to
break the bonds between atoms in a
compound
Bond Strength
The greater the difference in electronegativities, the greater the bond strength
BONDING OPTIONS• By transferring electrons
(producing ions)(big difference in EN)
• By sharing electrons(small difference in EN)
IONIC BONDbond formed between
two ions by the transfer of electrons
(difference in EN > 1.67)
IONIC COMPOUNDsubstance formed when electrons are
transferred between 2 or more substances
(making ions)
COVALENT BONDbond formed by the sharing of electrons
(difference in EN < 1.67)
MOLECULEa neutral group of
atoms held together by covalent bonds
(ex: H2O)
WHICH IS STRONGER?
Ionic bonds are stronger than
covalent
Bonds in all the polyatomic ions and
diatomics are all covalent bonds
IONIC BONDbond formed between
two ions by the transfer of electrons
IONIC COMPOUNDsubstance formed when electrons are
transferred between 2 or more substances
(making ions)