Chapter 6 Flashcards
Covalent bonds
The bonds between non-metallic atoms
Chemical properties of covalent melcules
Low melting and boiling temperatures because they are gases
Poor conductors of electricity due to no mobile charge particles
Ignite easily
Gases or liquids at room temperature
Covalent molecular element
Made up of identical atoms held together by covalent bonds including diatomic molecules
Covalent molecular compounds
Any compounds containing covalent bonds
Lone pairs
Two dots arranged as a pair
Bonding pairs
Single dots (unpaired) are available for sharing
Structural formula
When bonding pairs are replaced by a dash to make a diagram
Different molecular shapes
Pyramidal Tetrahedral V-shaped Linear Planar
VSEPR theory
Valence shell electron pair repulsion theory takes into account the spacing between the lone pairs and the bonding molecules to create the correct molecular shape
Prefixes
1 - mono 2 - di 3 - tri 4 - tetra 5 - penta 6 - hexa 7 - hepta 8 - octa 9 - nona 10 - deca
Rules for naming molecular compounds
- The first element is named in full
- second element is named as an anion with -ide
- Prefixes are used to show how many each have
The Pauling scale of electronegativities
- Electronegativities increase from left to right within a period.
- Electronegativities decrease from top to bottom within a group.
- Metals generally have lower electronegativities than non-metals.
Non polar covalent bonds
When two atoms of the similar elctronegativites are bonded together and share the elcetrons equally between them
Polar covalent bonds
When two atoms of different electronegativities are bonded together and share the electrons unequally between the atoms
Non-polar molecules
In non-polar molecules, the atoms have equal electronegativity and share electrons equally ot they are arranged in a way that cancels each other out
Polar molecules
When the overall charge is polar because the bonds are polar and the molecule is arranged in a way that doesnt balance out
Which molecular shapes are polar?
V-shaped or pyramidal molecules
Which molecular shapes are non-polar?
Linear, planar and tetrahedral
Intramolecular attractions
The bonds between the atom ie; covalent, metallic and ionic
Intramolecular forces
The forces between molecules of a covalent molecular compound
Different intramolecular forces
Dispersion
Dipole-Dipole
Hydrogen
Dispersion forces
Occurs between all molecules
The weakest of the forces
The more electrons in the molecules the stronger the dispersion forces
The shape of the molecule affects the forces as a liquid state will hold the molecules together closer than gas
Dipole-Dipole
Only occurs between polar molecules
Stronger force and causes higher boiling point
When the positive side of one molecule attracts the negative side of another molecule
Hydrogen bonding
Occurs between two molecules in which hydrogen is bonded to nitrogen, oxygen or fluorine.
Strongest force
Because the hydrogen (positive end) is unshielded, the other dipole can approach far more closely. The closer the dipoles get, the stronger the bond that forms
Properties of molecular compounds
Non-conductors because they are electrically neutral
Polar molecules dissolve in water because water is polar
Low mp/bp because of weak intermolecular forces
Soft and easily scratched
