prelim Flashcards
relative abundance
the percentage of that isotope in the naturally occurring element
Isotopes
Atoms of the one element that have different numbers of neutrons in their nuclei. Named by mass number
Prefixes
one - mono two - di three - tri four - tetra five - pent six - hex seven - hept eight - oct nine - non ten - dec
Nomenclature of Covalent Compounds
- more electronegative element last
- last element has suffix -ide
- prefix denoting number of atoms
Nomenclature of Ionic Compounds
- Cation first, anion second
- Monoatomic anions
- suffix ide
Polyatomic anions
- unique names - Cations
- oxidation state for atoms that may have several
Non-metal properties
- solid or gas at room temp
- dull/non-lustrous
- poor conductors
- neither malleable nor ductile
Properties of Metals
- solid at room temp
- shiny, lustrous
- good conductors of heat/electricity
- malleable and ductile
Gravimetric Analysis
- analysis by mass
Heterogenous mixture
composition varies throughout mixture
Emission Spectrum
when an atom has electrons in higher levels that can move down to lower levels, they emit photons with an energy based on the difference in electron levels
- as electrons move, excess energy is emitted as light
Ionisation Energy
The energy required to remove an electron and form an ion
Homogenous mixture
uniform in composition
physical properties - definition
characteristics of a substance that can be observed without changing it into a different substance
Flame Test colours
copper - green calcium - red strontium - red barium - green potassium - purple sodium - yellow (cations cause colour)
Sulphate
(SO4)2-
Hydroxide
(OH)-
Carbonate
(CO3)2-
Sulphite
(SO3)2-
State of Matter - periodicity
solid to gas across a period
Unstable Isotopes
release radiation to become more stable. Atomic number >83
Physical properties to separate mixtures
- filtration
- solubility
- boiling point
- evaporation
- distillation
- density
- sedimentation
- decanting
Characteristics Used to identify substances
- colour
- magnetism
- melting and boiling points
- density
Nitrate
(NO3)-
Nitrite
(NO2)-
Alpha
- helium nucleus
- low penetrative ability
- decays as there are too few neutrons to be stable
Detoxifying Poisonous Foods
Cycad Fruit - leaching - fermentation Black Beans - heat seeds - scrape into finer portions - soak in water - mash then bake
Leaching
- grind/pound kernels
- soak in water
- ground then bake
- salt sometimes used
Fermentation
Stored for months in a moist environment
Beta
- electron
- medium penetrative ability
- decays as there are too many neutrons to be stable
Gamma
- no particle is released, instead electromagnetic radiation
- high penetrative ability
- decays from an unstable atom releasing energy
Phosphate
(PO4)3-
Intermolecular forces
forces that act between molecules
- dipole-dipole
- dispersion
- hydrogen bonding
Intramolecular forces
- forces that act within the molecule
ionic bonding
- atoms exchange electrons to achieve noble gas configuration
covalent bonding
atoms share electrons to gain noble gas configuration
ionic substance properties
- solids at room temp
- high melting and boiling points
- hard and brittle
- don’t conduct electricity as solids
- when molten or in aqueous solution, they do conduct electricity
Covalent molecular substance properties
- generally gases or liquid at room temp
- low melting and boiling points
- soft as solids
- pure covalent don’t conduct electricity
- in aqueous solution do conduct electricity
why do ionic substances have those properties?
- much energy is needed to break up electrostatic forces between ions
- ions are tightly bound and unable to move towards a charged electrode, therefore do not conduct electricity
why do covalent molecular substances have those properties?
- bonding forces holding the atoms together within the molecule are very strong, but intermolecular forces are easily broken, hence lower boiling and melting points
covalent network solids
- covalent bonding extends indefinitely throughout
- don’t conduct electricity except graphite
metallic bonding
- metals all have a common structure
- 3D array of positive ions held together by a mobile ‘sea’ of delocalised electrons
polar covalent bonds
electrons are unequally shared
dipole-dipole forces
the attractive electrostatic forces between polar molecules
dispersion forces
weak intermolecular forces that arise from electrostatic attractions between instantaneous dipoles in neighbouring molecules