Structure and Bonding Flashcards
What are the processes when matters change?
Gas → condensing → liquid → freezing → solid → melting → liquid → evaporating → gas
Solids
Fixed shape and volume
Cannot be compressed
Liquids
Fixed volume but can flow and change their shape
Occupy slightly more space than when solid
Gases
No fixed shape or volume
Can be compressed easily
Gas to liquid
Hotter solid → faster particles vibrate
Vibrations so strong particles break free from neighbours
Solid starts to melt as particles separate
Liquid to gas
Gas condenses to liquid
Hotter a liquid is, faster particles move
Temperature rises → more and more energy is transferred from surroundings to particles
Particles escape from surface of liquid
Rate of evaporation increases
Liquid boils and bubbles of gas rise and escape within liquid
Difference of electrons between covalent bonding and ionic
Sharing electrons = covalent
Transferring electrons = ionic bonding (loses or gains so positively charged as electrons are being transferred elsewhere)
What groups gain and lose electrons?
Groups 5, 6, 7 = gain electrons
Groups 1, 2, 3 = lose electrons
Ionic Bonding
Transferring of electrons between a metal and a non-metal → makes an ion because it gains/loses electron
Lattice
Strong electrostatic forces broken when melted or boiled
High melting and boiling points = lots of energy to break electrostatic forces of attraction between oppositely charged ions
Ionic Bonding Electricity
Can conduct electricity only when molten or dissolved = have charged ions but not free-moving
Ions move around because electrons aren’t delocalised = fixed place within shells so ions move
Giant Ionic Structures
High melting point
High boiling point
Because strong electrostatic forces use lots of energy to break ions
Only conducts electricity when molten or dissolved → ions in fixed positions in lattice, no freely moving charged particles
Greater change of ions, stronger the forces holding them
Covalent Bonding
Low melting and boiling points
Share electrons between 2 non-metals
Making atoms stable
e.g. water and oxygen
Intermolecular forces
Forces between small molecules
Intermolecular forces = weaker than covalent bonds
When small molecular substances melt or boil = weak intermolecular forces are broken
Attraction between individual molecules = weak intermolecular forces
Does not take a lot of energy to break
Intermolecular forces increase with size → larger molecules → higher melting points
Compounds made of simple molecules do not conduct electricity unless aqueous because there is no overall charge
Neutral molecules cannot carry electrical charge
Simple Covalent Structure
Held together by intermolecular forced of attraction
Sharing of electrons
Melt and boil → intermolecular forces break
Water
Giant Covalent Structure
Held together by covalent bonds
Diamond
Melting and boiling = covalent bonds break → lots of energy
Can’t conduct electricity → no free-moving charged particles
Bonding in Graphite
Layers of carbon
Held together by covalent bonds → takes lots of energy to break
Carbon in group 4
1 electron is not attached to other carbons, so is free to move through structure
Melting and boiling points = don’t melt and boil because still have giant covalent structure
→intermolecular forces break when melts/boils (little energy)
→layers can then slide over each other
Electricity = electrons delocalised → have negative charge and are free moving
Metallic Bonding
Atoms arranged in regular patterns
Electrons in outer shell of metal delocalised → free to move throughout whole structure
Electricity = because electron is negatively charged and can move → free moving charged particles so can conduct
Metal and boiling points = have to separate atom from structure → takes lots of energy
Pure Metals
In layers
Slide over each other → so they are soft
Alloys
Mixture of two or more elements with at least one being a metal
Distorted layers
Cannot slide → so they are hard
Explaining Properties of Metals
Negative charge between positive ions, holds the metal ions in place
Delocalised electrons enable the lattice to distort
Ductile
High melting points = electrostatic forces of attraction are in all directions so takes a lot of energy to break and melt the metal
What are nanoparticles made from?
Lots of different atoms
Risks of using nanoparticles
Effective as catalysts
Risk of finding their way into atmosphere
Unpredictable effects
Few health risks