Chapter 6- Covalent Bonding Flashcards
What sort of electronegativity do non-metalliac elements have?
Generally high
How do non-metalliac elements get a full shell of electrons when reacting with another non-metalliac element?
Share electrons
What does the sharing of electron pairs produce?
A covalent bond
What are non-bonding elecrtrons referred to in reagrds to electron dot diagrams?
Lone pairs
How do you draw electron dot diagrams?
All inner shell electrons are replaced by elements symbol and the outer shell electrons are represented by dots.
Rules for Drawing Electron Dot Diagrams
- Draw the dot diagrams for each of the atoms in the molecule.
- Unpaired electrons are avaliable for sharing to form a covalent bond.
- Paired (lone pairs) do not participate in the bonding.
- The atom with the most bonding electrons is placed in the centre, with other atoms bonded to it.
What simple is used to represent a shared pair?
-
How many maximum bonds can it have?
Three
Name the five common shapes of common molecules
- Tetrahedral
- Pyramidal
- V-Shaped
- Linear
- Planar
Steps in naming a non-metalliac molecule
- The first element in the formula is named in full
- The second element is named as if it is an anion and is given an -ide suffix
- The number of each type of atom in the molecule is indicated by a prefix
Define non-polar covalent bonds
Bonding electron pairs is shared equally and is distributed evenly between the two nuclei.
In which elements does non-polar covalent bonds exist?
- The same elements
- Elements with the same electronegativity
When do polar covalent bonds occur?
When the bonding of electrons are unequally shared
Explain polar covalent bonding
The elements will have different electronegatives. The shared electrons will move closer towards the element with higher electronegativity, thus creating a negative charge on this side of the molecule. Therefore the other side becomes slightly postively charged.
What is the charge seperation of polar covalent bonding also known as?
Dipole-dipole
Is a polar covalent bond ever truely covalent?
NO
What happens when there is a greater difference of 2.0 in the molecules electronegatives?
An ionic bond forms
What determines a polar molecule?
One end is slightly positive and the other is slightly negative.
What are the rules for determining polarity?
- Draw an electron dot diagram of the model
- Apply the vespr rules to draw the shape of the diagram
- Use electronegatives to determine bond dipoles
- Use the shape to determine whether bond dipoles cancel out
Define intramolecular bonding?
Bonding within molecules
Define intermolecular bonding?
Bonding between molecules
Define intermolecular force
The force of attraction between molecuels
Explain the relationship betwen moleculer force and the boiling point?
The stronger the molecular force the higher the boiling point.
What are the three types of intermolecular bonding?
Dipole-Dipole
- Dispersion
- Hydrogen Bonding
Explain dispersion forces
- Occur when nuclei attract electrons from neighbouring atoms attract electrons
- At any point in time the electrons can be found on either side of the moelcule.
- All molecules have dispersion forces
Explain dipole-dipole interactions
- The positve side of a molecule attracts a negative side of another molecule
- Have dispersion forces aswell
What is hydrogen bonding a special case of?
Dipole-dipole interactions
Explain hydrogen bonds
When hydrogen bonds to FON the electrons move slightly towards that atom leaving hydrogen exposed.
-Hence another dipole can come alot closer to the hydrogen and have alot stronger bond
What are the strongest type of bonds?
Hydrogen
What is the overall charge on a covalent molecule?
0
Define non-polar covalent bonds
Formed between atoms with the same electronegavitiy or they are the same element.
Define polar covalent bonds
Electrons are unequally shared
-Elements have different electronegatives
What are non-polar molecules?
Only non-polar bonds
What defines a polar molecule?
One end is slightly negative and the other is slightly postive.
What sort of bonding occurs in all forms of water?
Hydrogen
Explain the unusualness of waters properties
- It expands upon freezing.
- It has a very high melting point compared with other substances
Why does ice float in water?
The open hexagonal crystalline lattice move the water molecules furthur apart than the liquid state, because water expands on freezing this means it has a lower density in the solid form, hence the ablity to float.
What is a discrete molecule?
A covalent molecule in which the intermolecular forces are really weak
What physical properties do intermolecular substances have?
- low melting point and boiling point due to weak intramolecular forces
- liquid or gaseous at room temp
- do not conduct electrcity
