Covalent Bonding Flashcards
What is a covalent molecular substance?
Molecules held together by covalent bonds, where the attraction between the molecules is weak and there are no charged particles.
Different elements are in the molecule.
eg Co2 gas
What is a molecule?
Group of non metallic atoms held together by covalent bonds. Theyre combined in a fixed ratio and are neutral
What is a covalent molecular element?
Identical atoms held together by covalent bonds- theyre discrete as theyre all seperate
What is covalent bonding?
Bonding between non metals where they share pairs of electrons to get full outer shell.
What is a covalent bond between?
Similtaneous attraction between two positive nuclei and the same shared pairs of electrons
Outline VSEPR
The electron pairs in molecules repel each other and take up positions as far away from one another as possible.
What does VSEPR stand for
Valence Shell Electron Pair Repulsion theory
What are binary molecular compounds?
Compounds where there are only 2 elements in it
eg water c02 methane
How do we name an molecular substance?
First ones named fully then second element names as an ide. Use prefix for the elements.
eg Carbon Di-oxide
Di hydrogen Oxide
Nitrogen Tri Bromide
What is another definition for electronegativity?
Relative attraction that an atom has for shared electrons in a covalent bond.
What are non polar covalent bonds?
Two atoms of same/equal electronegativity simaltaneously attract shared pairs of electrons
What are polar covalent bonds?
Covalent bonds where the bonding electrons are unequally shared. Electrons are therefore unsymmetrically distributed
what is a bond dipole?
In a polar covalent molecule one end becomes slightly more positive and one slightly more negative. this seperation is a bond dipole
What level of difference in electronegativities causes each of the bonds?
0 up to 0.4= non polar
0.4 up to 2= polar
2 or more= ionic
What is a polar molecule?
One end of the molecule is slightly positive and one end is slightly negative. Contains polar bonds and is
called a Dipole
Whats a non polar molecule?
Molecule containing only non polar bonds
What is the difference between intra and inter molecular bonding>
Intra-molecular bonding is inside molecules, so covalent bonds, and inter molecular bonding is between the molecules so dispersion etc.
What is the purpose of intermolecular bonding?
Determines state of molecule usually
What is the golden rule of intermolecular bonding?
The stronger it is the higher the b and m point of a substance.
What are dispersion forces?
2 types
- All electrons of an atom are attracted by all neighbouring nuclei.
- Instantanous dipoles occur where at any time there’s a chance electrons could be on one side of an atom causing an induced dipole.
Whats the problemo with dispersion forces?
For them to really have much of an effect, the atoms need to be slowed down and they’re pretty weak.
What makes dispersion forces stronger?
- Size of molecule. as it increases dispersion forces are stronger
- Shape of molecule. The closer they can get the stronger the dispersion forces.
What are dipole-dipole interactions?
If molecules are polar in a sample, the slightly oppositely charged ends attract each other .
What is hydrogen bonding?
Special case of dipole dipole attractions
When hydrogen bonds to a more electronegative element the h nucleus is left unsheilded!!
only occurs with F O and N
Stronger than regular dipole dipole by far
Why is hydrogen bonding to blame for waters properties? Name 3 properties and why
High melt and B points due to strong h bonds holding atoms together
Expands on freezing- Open hexagonal lattice of ice plates puts them further apart then in the liquid state.
Ice forms layer on top that insulates the cooler water below. Why is this good?
fishies
What is the general rule for solubility of molecular substances?
Like disolves like.
Polar water dissolves polar molecular substances for eg
Do Molecular substances have high or low melting points? Why?
Low melting points, as intermolecular forces are weak. Most are gasses or liquids at room temp.
