Topic #2: Bonding and structure Flashcards
What are the 3 bond types?
Covalent- sharing electrons
Ionic- giving electrons
Metallic- pulled together by charges
When does each bond type occur?
Covelant- Nonmetal and Nonmetal
Ionic- Metal and Nonmetal
Metallic- Metals/alloys
Metals that lose electrons become _______ charged ions.
Positively
How are ionic compounds (giant ionic lattices) held together?
Strong electrostatic forces of oppositely charged ions
Can covalent bonds contain small molecules?
Yes
Are covelant bonds strong or weak?
Strong
Are polymers covelantly bonded?
Yes
What causes the strong metallic bonds?
Free to flow delocalised electrons
When do things change state of matter?
Freezing and melting at melting point
Boiling and condensing at the boiling point
How does the strength of the bonds affect melting points?
The stronger the bond, more energy is needed to break it (higher melting point)
List the 4 state symbols
g - gas
l - liquid
s - solid
aq - aqueous in solution
Why are ionic melting points so high?
Many very strong electrostatic forces of attraction are hard to break
Why can molten ionic compounds conduct electricity?
The ions are free to move
Are boiling points for small molecules high or low, and why?
Low, because only weak intermolecular forces need to be broken, not the covelant bonds.
How does molecule size impact intermolecular force strength?
The larger the molecules the stronger the bond
Do polymers have high or low melting points?
High- they are large molecules
What are the melting points for giant covelant structures like?
High, there are very strong bonds
Why are alloys harder than pure metals?
Different size atoms disrupt smooth slidy layers
Do all metals have high melting points?
No
Why are metals good conductors?
They can carry charge and energy in the delocalised electrons
Describe diamond’s structure.
4 hexagonal carbon bonds, very strong, no conduction, high melting point, hard
Describe the structure of graphite.
3 Carbon bonds, with one delocalised electron per atom to carry charge. No bonds between layers, soft.
What are fullerenes?
Hexagonal carbon structures (can be rings of 5 or 7) made of carbons, useful in nanotechnology
What is graphene?
A single layer of graphite, useful in electronics
What are the size boundaries for nanoscience?
1-100 nm
What are the size of fine and coarse particles?
Fine, 100-2500 nm
Coarse, 2500-10000 nm
If the sides of a cube decrease by 10 times what does the surface area to volume ration increase by?
10 times
Why use nanoparticles over bulk metal?
Nanoparticles have larger surface areas, meaning less is needed, and they have different properties
What can nanoparticles be used for?
Suncreams, electronics, cosmetics, medicine, catalysts and deodorants
