Topic 3 - structure and bonding Flashcards
What is ionic bonding
Ionic compounds being held together by strong forces of attraction between their oppositely charged ions.
What are the particles like in a solid?
- packed close together
- vibrate around in fixed positions
What are the particles like in a liquid?
- close together but can slip and slide over eachother in a random motion
What are the particles like in a gas?
Lots of space between them and zoom around randomly
Why do the simple particle models have limitations?
The atoms, molecules and ions that make up all substances are not solid spheres with no forces between them
Elements form compounds by…
…Gaining or losing electrons by sharing electrons
Name the groups and what ions they form
- group 1 forms 1+ ions
- group 2 forms 2+ ions
- group 3 forms 3+ ions
- group 4 don’t form ions (except Sn and Pb)
- group 5 forms 3- ions
- group 6 forms 2- ions
- group 7 forms 1- ions
- group 0 never forms ions
Why will ionic compounds conduct electricity when molten or dissolved in water?
Their ions can then become mobile and can carry charge through the liquid
Why do ionic compounds have high melting points?
It takes a lot of energy to break the strong ionic bonds, operating in all directions, that hold a giant ionic lattice together
When are covalent bonds formed?
When atoms of non-metals share pairs of electrons with each other
Many substances containing covalent bonds consist of s……… m…………….. but some have g……. c…………. structures
Simple molecules, giant covalent
Substances made up of simple molecules have ……… melting and boiling points
Low
Why do the substances of simple molecules have low melting and boiling points?
Because the intermolecular forces between them are weak
Simple molecules have no overall charge so they can’t what?
They can’t carry electrical charge and cannot conduct electricity
Giant covalent substances have very ……. melting and boiling points
High
Why is graphite soft and slippery?
It contains giant layers of covalently bonded carbon atoms, however there aren’t any covalent bonds between the layers meaning they can slide over eachother.
What is a diamond like, in terms of atomic structure?
The carbon atoms have a rigid giant covalent structure, therefore diamonds are a very hard substance
Why can graphite conduct thermal energy and electricity?
Because of the delocalised electrons that can move along it’s layers
Describe fullerenes
- large, cage-like structures and tubes based on hexagonal rings of the carbon atoms
What can fullerenes be used for?
- transport mechanism for drugs to specific sites in the body
- as catalysts
- reinforcement for composite materials
Why can metals be bent and shaped?
The layers of atoms (positively charged ions) in a giant metallic structure can slide over each other
What are alloys like and why?
- harder than pure metals because the regular layers are distorted by atoms of different sizes in an alloy
Why do nano particles have properties different for the same materials in bulk?
Because nano particles have a high SA:V ratio, with high percentage of atoms exposed at the surface
What is nano science?
The study of small particles between 1 and 100 nanometres in size
