Chapter 6 Section 1. Sharing Electrons Ionic bond: Electrons transfer from one atom to another to...
-
Upload
earl-elliott -
Category
Documents
-
view
213 -
download
1
Transcript of Chapter 6 Section 1. Sharing Electrons Ionic bond: Electrons transfer from one atom to another to...
Chapter 6
Section 1
Sharing Electrons
• Ionic bond: Electrons transfer from one atom to another to form ions
• Covalent bond: Sharing of electrons between atoms
– Example: water
– O2 + 2H2 2H2O
Molecular Orbitals
• 2 Hydrogen atoms approach each other
– The nucleus of each atom attracts its own electron and the electron of the other hydrogen atom
– The nucleus repel each other and the electron clouds repel too
– There isn’t enough attraction to take electrons away so they share
– Form a single electron cloud around by Hydrogen nuclei
Molecular Orbitals
• After they share electrons we have H2
• Both Hydrogen atoms are now stable because of the shared electrons
• Covalent bond: Forms when two or more valence electrons are shared between atoms
Molecular Orbitals
• Single Bond: – Two atoms share one pair of electrons
• Molecular orbital:– Space around the two nuclei where shared
electrons are moving
Covalent Bonds
• Nuclei bonded together are not a fixed distance from each other– They vibrate back and forth coming closer
and then stretching further apart
• Bond length:– The average distance between two bonded
atoms
Covalent Bonds
• Once the nuclei are bonded together are they permanently bonded together?– No!– If the bond energy is reached the bond can break and
the two nuclei are no longer bonded
• Bond energy:– Energy required to break a bond between two atoms
and separate them– Typically stronger bonds the bond length is short– Generally the highest bond energy comes when
atoms are bonded to H and F
Electronegativity and Bonding
• Electronegativity:– Tendency of an atom to attract bonding
electrons to itself when it bonds with another atom
– Table 6-2 Electronegativity values– Values generally increase as you go left to
right across a period– Down a group values decrease
Electronegativity and Bonding
• Nonpolar covalent bond:– Bonding electrons are shared equally– H bonded to H– Electronegativities of two atoms are equal
• Polar covalent bonds: – 2 atoms form a covalent bond but one atom attracts
electrons more strongly than the other– Attraction is not strong enough to transfer the electron
to the other atom though
Electronegativity and Bonding
• If the electronegativities are greatly different than an ionic bond forms
• Figure 6-7 page 199
Determining Ionic or Covalent
• The difference between the electronegativities is what is important– Difference greater than 2.1 the bond is ionic
– Difference between 0 and .5 the bond is nonpolar covalent
– Difference between 0.5 and 2.1 the bond is polar covalent
Examples
• Is the compound AlF3 ionic or covalent
• Is the compound AlCl3 ionic or covalent
Polar Molecules
• Polar:– Suggests that the ends have opposite
charges such as a battery or magnet
– Example: HF • F gets the – charge• H gets the + charge
• Dipole:– One end has a partial positive charge and the
other has a partial negative
Dipole Moment
• As the polarity of the molecule increases its bond strength also increases
• A larger dipole moment indicates a higher degree of polarity