Chapter 9 Covalent Bonds pp. 240 - 267
- Force that holds two atoms together
- An electrostatic force that holds oppositely charged particles together in an ionic compound
- What are atoms and compounds always trying to achieve?
- Complete set of valence electrons…
What is a covalent bond?
- Chemical bond that results from sharing of valence electrons
Which bond is stronger?
- Ionic compounds are in a crystal lattice…many ions are bonded together in a crystal lattice
- Covalent compounds are neutral and often found in the form of individual molecules
- Ionic bonds are stronger than covalent bonds
How are covalent bonds formed?
- Charge of electron cloud?
- What happens when 2 fluorine atoms approach each other?
- Covalent bond occurs at “Point of maximum attraction”
- Attractive forces of nucleus for electrons and repulsive forces of electrons in each atom balance out
- What would happen if the atoms kept moving closer?
What is a Molecule?
- Compound made when two or more atoms bond together covalently
- In nature, sometimes two atoms of the same element are more stable when they are covalently bonded than the individual atom alone…
- Br 2 I 2 N 2 Cl 2 H 2 O 2 F 2
Types of electrons in molecule
- What is the electron configuration?
- How many Valance electrons?
- What would two F atoms look like covalently bonded?
- BONDING PAIRS are electrons involved in the covalent bond (shared electrons)
- The pairs of electrons that are NOT involved in the covalent bond are called the LONE PAIRS (unshared electrons)
- What are the lone pairs in…
In the fluorine molecule…
- How many bonding pairs are there in each?
- How many lone pairs are there each?
Lewis Dot Diagrams
- When writing out molecules…
- Bonding pairs can be represented by the electrons themselves or by a single line
- If there is more than one bonding pair, two lines are used
- Up to four lines can be used
- EACH LINE REPRESENTS A BONDING PAIR OF ELECTRONS IN A MOLECULE
- Lines represent bonding pairs…you must still draw out lone pairs
3 basic rules
- Sum up valence electrons of all atoms in the molecule
- Use a pair of electrons to form a bond between atoms…use a line to represent bond
- Arrange remaining electrons to satisfy the duet rule for hydrogen and the octet rule for other atoms
- (Verify that each atom has a complete set of electrons )
- Elements is group 7A have how many valence electrons?
- How many electrons would they share in a covalent bond with an atom in group 7A?
- How many covalent bonds do are formed between bonding atoms in 7A?
- Elements in group 6A have how many valence electrons?
- How many electrons would they have to share in a covalent bond with another atom in group 6A?
- How many covalent bonds do are formed between bonding atoms in 6A?
- Elements in group 5A have how many valence electrons?
- How many electrons would they have to share in a covalent bond with another atom in group 5A?
- How many covalent bonds do are formed between bonding atoms in 5A?
- Elements in group 4A have how many valence electrons?
- How many electrons would they have to share in a covalent bond to be stable?
- How many covalent bonds are formed between bonding atoms in group 4A?
Writing Chemical Equations showing covalent bond formation
Classwork…to turn in… 6. HF 7. N 2 8. CH 4 9. CF 4
- Show the formation of the following molecules…your final answer should be the correct Lewis Dot Structure