C2 - Bonding, Structure And Properties Of Matter Flashcards
What are ions
They’re charged particles - single atoms or groups of atoms
When atoms lose or gain electrons they form ions
Loose electrons - positive ions
Gain electrons - negative ions
Which groups are most likely to form ions
Groups 1,2,6,7 as they either need to gain or lose 1 or 2 electrons
E.g sodium atom loses 1 electron to form Na+ so it’s
Na -> Na+ + e-
Oxygen atom gains 2 electrons to form O2- so it’s
O + 2e- -> O2-
What is ionic bonding
Transfer of electrons
When a non metal and metal react together, the metal atom loses electrons and the non metal gains them - these oppositely charged ions are attracted by electrostatic forces - ionic bond
Share electrons
How to show ionic bonding
Dot and cross diagram - show arrangement of electrons in an atom or ion
One atom gives up an electron to the other atom so they both have a full outer shell
Dot and cross show how they’re formed, but not structure, size of ions or arrangement
What are ionic compounds
Ionic compounds(have regular lattice structure) have a structure called a giant ionic lattice Ions Form closely packed regular lattice arrangement with very strong electrostatic forces of attraction between oppositely charged ions, In all directions of the lattice
Different models for ionic compounds compounds
Ball and stick model - shows regular pattern of ionic crystal and shows how ions are arranged - not to scale - no gaps
Another model shows size and pattern of ionic crystal - only see outer
See notes for diagram
Properties of ionic compounds
All have high melting/boiling points due to strong bonds between ions - lots of energy to overcome
When solid, ions are held in place - can’t conduct electricity
When melted, ions can flow and carry current
Dissolve easily in water - ions separate and flow
How to find empirical Formular on an ionic compounds from diagram of compound
Dot and cross - count atoms of each element and write down for empirical Formular
3D Model - work out what ions are in the ionic compounds and balance charges of ions so overall charge of compound is 0
What is covalent bonding
Sharing electrons (only outer shells) When non metals bond together, they share pairs of electrons to make covalent bonds
Why are covalent bonds strong
Positive charged nuclei of bonded atoms are attracted to shared pair of electrons by electrostatic forces
What does each single covalent bond provide
Provides one extra shared electron for each atom
Each atom involved makes enough covalent bonds to fill up its outer shell
Covalent bonding happens in compounds of non metals and non metal elements
Different ways of drawing covalent bonds
Dot and cross - show bonding in covalent compounds. Electrons overlap and show which atom the electrons in a covalent bond comes from - no size or arrangement
Line model - displayed Formula and shows CB as a single line
Good for showing how atoms are connected in large molecules - no 3D structure or which atoms the electrons in the cb come from
3D Model - shows atom, CB and their structure - confusing for large molecules with lots of atoms. Doesn’t show where electrons in the cb came from
What are simple molecular structures made up of
Made up of molecules containing few atoms joined with covalent bonds
Common examples of simple molecular structures
Hydrogen H2- has 1 electron needs one more - form single cb
Chlorine Cl2- each Cl needs one more electron - two chlorine share one pair
Oxygen O2- needs 2 more electrons - share two pairs to form double cb
Nitrogen N2 - needs 3 more - 2 nitrogen share 3 pairs - triple bond
Methane CH4 - carbon has 4 - half - form 4 cb with hydrogen
Water H2O - oxygen shared pair with 2 hydrogen to form 2 single cb
Hydrogen chloride HCl - needs one more
See notes for diagrams
Properties of simple molecular structures
Substances with covalent bonds normally have simple molecular structures
Atoms within molecules held together with very strong covalent bonds - forces of attraction are weak
Low melting/boiling as the forces of attraction are weak - particles easily separated
Most gases or liquid at room temperature
As molecules get bigger, their intermolecular forces increase - more energy to break
Don’t conduct electricity - no free electrons or ions
What are polymers
Long chains of repeating units
Lots of small units linked together to form a long molecule
All atoms in a polymer are joined with covalent bonds
How do you draw a polymer
Just draw the repeated section in brackets - bonds through brackets
See notes for diagram
‘n’ next to brackets represents how many repeats
How to find molecular formula of a polymer
Write unit in bracket with n
For poly(Ethene) molecular formula is C2H4 See notes for diagram
Properties of a polymer
Intermolecular forces between polymer molecules are larger than the simple covalent molecules - more energy needed
Most polymers solid at room temperature
Intermolecular forces weaker than ionic or covalent bonds - lower boiling points
How are atoms bonded in giant covalent structures
With strong covalent bonds
What are giant covalent structures
They are macromolecules
Properties of giant covalent structure
High melting/boiling points - lots of energy
Don’t contain charged particles - can’t conduct electricity, even when molten
Examples of giant covalent structures (diamond, graphite, silicon dioxide)
Diamond - each carbon atom forms 4 cb in a very rigid giant covalent structure
Graphite - each carbon atom forms 3 cb to create w layer of hexagons
Each carbon atom has one delocalised (free) electron - can flow
Silicon dioxide - sometime scaled silica - what sand is made of - each grain of sand is one giant structure of silicon and oxygen
What’s an allotrope
Different structural forms
Properties of diamond
Diamond has a giant covalent structure made up of carbon stoke that form 4 cb- very hard
Strong cb take lots of energy to break - high melting point
Doesn’t conduct electricity - no free electrons or ions
Properties of graphite
Each carbon atom forms 3 cb creating a sheet of carbon atom arranged as hexagons
No cb between layers - held weakly and free to move over - soft and slippery - lubricating material
High melting point - cb in lagers need lots of energy to break
Can conduct electricity due to delocalised electron
What is Graphene and properties
Graphene is one layer of graphite
Still 3cb forming hexagons
CB make it strong. Very light - added to composite materials to improve strength without adding weight
Still conduct electricity due to delocalised electron
What are fullerenes
Fullerenes form spheres and tubes
They’re molecules of carbons shaped like tubes or hollow balls
Carbon atoms arranged as hexagons, but can contain pentagons or heptagon
Properties/uses of fullerenes
Used to cage other molecules - structure forms around other atom or molecule - deliver drug in body
Huge surface area - good industrial catalyst
Good lubricants
Fullerenes form nanotubes - tiny carbon cylinders - conduct electricity and thermal
High tensile strength (strength when stretched)
‘Nanotechnology’
What does metallic bonding involve
Involves delocalised electrons
Metals consist of a giant structure
What is metallic bonding
Strong electrostatic forces of attraction between positive metal ions and negative share electrons
Hold atoms together in a regular structure
What substances are held together by metallic bonding
Metallic elements and alloys
What produces all the metals properties
Delocalised electrons in the metallic bonds
Properties of most metals
Electrostatic forces between metal atoms and delocalised sea of electrons are very strong - high melting/boiling point
Metals area good conductors of electricity and heat
Delocalised electron can carry current and thermal energy through whole structure
Metals are malleable - layers of atoms in metals can slide over each other
What are alloys
Alloys are harder than pure metals as they’re a mixture of two or more metals of metal and another element (pure metals are too soft)
What makes alloys harder
As the different elements are different sized atoms, an element mixed with a pure metal will distort layers meaning it’s harder to slide over each other
See notes for diagram
Properties of solid
Strong forces of attraction between particles - held in fixed positions to form regular lattice structure - vibrate around fixed positions - definite shape
Properties of liquid
Weak forces of attraction
Randomly arranged and free to move but close together
Definite volume but no definite shape
Constant movement in random directions
Properties of gas
No forces of attraction
Free to move and far apart
Constantly moving at random directions quickly
No definite shape or volume
Hotter = faster and more pressure or expansion
What’s aqueous
Dissolved in water
Name the changes of state
Solid > gas sublimation Gas > solid decomposition Solid > liquid melting Liquid > solid freezing Gas > liquid condensing Liquid > gas boiling/evaporating
