CHEMISTRY C2

STRUCTURE AND BONDING

• Chemical bonding involves either transferring or sharing electrons in the highest occupied energy levels (shells) of atoms in order to achieve the electronic structure of a noble gas.
• •Covalent: Non-Metal + Non-Metal (e- Shared)
• •Ionic: Metal + Non-Metal (e-donated/accepted)
• •Metallic: Metals
• Atoms that lose electrons become positively charged ions.
• Atoms that gain electrons become negatively charged ions.

STRUCTURE AND BONDING- GIANT IONIC

• High
• MBP
• •Strong
• Ionic bond
• •due
• to strong electrostatic attraction.
• •Giant ionic lattice
• •Therefore
• Lots of energy to break bonds
• Conducts
• When Molten
• •When
• liquid Ions are free to move
• •Ions
• Can carry charge across molecule
• •When
• solid ions cannot move

STRUCTURE AND BONDING-Simple Covalent

• All
• covalent compounds except diamond, graphite and silicon dioxide
• Low
• MBP
• •Strong
• covalent bonds
• •Weak
• intermolecular forces
• –
• •Little
• energy required to break forces
• Don’t
• Conduct
• •No
• free electrons to carry charge

STRUCTURE AND BONDING-METALLIC

• High
• MBP
• •Giant
• Metallic
• •Strong
• metallic bonds (in layers)
• •As,
• positive ions floating in a sea of delocalised electrons
• •Electrons
• act like glue between positive ions
• •Lots
• of energy required to break bonds
• Conducts
• •Delocalised
• electrons
• •Can
• carry charge across molecule

STRUCTURE AND BONDING-GIANT COVALENT

• High MBP
• •(C) has(4) electrons on outer shell
• •(4) strong covalent bonds
• •To (4) other (Carbon) atoms
• •Therefore lots of energy needed to break bonds
• Don’t Conduct
• •No free electrons to carry charge
• *(_) is only for diamond

STRUCTURE AND BONDING-GRAPHITE

• Conducts
• •Each Carbon covalently bonded to3 other carbons
• •Therefore
• delocalised electron between layers
• •Can carry charge across the molecule
• Structure
• •Each Carbo covalently bonded to 3 other carbons
• •Weak
• inter molecular forces between layers
• •Layers
• slide off eachother
• easily

STRUCTURE AND BONDING-NANO PARTICALS

• •Size 1-100 nanometres (1 billionth of a metre).
• •Nanotubes work as lubricant because tubes slide over each other and there are weak forces
• between nanotubes
• •Nanoparticles have different properties to normal sized particles.
• •A few hundred atoms
• •Not all tested for safety yet.
• •Fullerenes are used as lubricants and for drug delivery
• •Nanotubes are strong with big surface area – so good catalysts and good at strengthening.

STRUCTURE AND BONDING-ATOMIC STRUCTURE

• •Mass number-top number
• •Atomic number-bottom number
• •The relative masses of protons is 1, neutrons is 1 and electrons are 1/2000
• •Mass number-protons + neutrons
• •Isotopes different numbers of neutrons of that element.
• •The
• relative formula mass (Mr) of a compound is the sum of the relative
• atomic masses of the atoms in the numbers shown in the formula.
• •The
• relative formula mass of a substance, in grams,is known as one mole of that
• substance.

ANALYZING SUBSTANCES

• Elements and compounds can be detected and
• identified using instrumental methods. Instrumental methods are accurate, sensitive
• and rapid and are particularly useful when the amount of a sample is very
• small.
• Chemical
• analysis can be used to identify additives in foods. Artificial colours can
• be detected and identified by paper chromatography.
• Describe paper chromatography
• •Sample
• carried up paper by solvent
• •Separates
• into constituent parts
• •Compare
• height (Rf
• value) to additive

ANALYZING SUBSTANCES-GAS CHROMATOGRAPHY

• •Helium
• carries substance through coil
• •Substance
• separates in coil (packed with solid)
• •Substances
• separated by speed
• •Position
• of peaks shows retention time, each peak
• is 1 compound
• •Substance
• passed into Mass Spectrometer
• •Mass
• spectrometer shows RMM (relative molecular mass) of parts of substance –
• identifies the substance