mod 1 Flashcards
Definition: Homogenous
is a mixture that is consistant throughout
Defintion: Mixture
an impure substance consisting of two or more elements or compounds that aren’t chemically bonded (impure homogenous and heterogenous substances)
Definition: Heterogenous
is a mixture with inconsistencies throughout
Definition: Solution
is a homogenous mixture
minor substance = solute
major substance = solvent
Definition: Colloid
a homogenous mixture with fine particles of an insoluble substance dispersed
Definition: suspension
is a heterogeneous mixture where large particles don’t dissolve in the solvent and sediment overtime
Definition: Gravimetric analysis/percentage composition
works out the composition of a mixture (write to the lowest sig figs in the question)
How are ionic bonds formed?
they are formed by the electrostatic attraction between cations (+) and anions (-) (metal and non metal)
How are covalent bonds formed?
they are formed when 2 or more elements (non-metals) share a pair of electrons
Memorise the polyatomic ions/radicals
nitrate/nitrite
hydroxide
hydrogen carbonate
carbonate
sulfate/sulfite
phosphate
ammonium/ammonia
Name some physical properties (properties observed without changing chemical properties or matter)
melting point
boiling point
lustre
malleability
ductility
electrical/thermal conductivity
Name the liquid and gas elements at room temperature (25C)
liquids: bromine, mercury
gases: helium, neon, argon, krypton, xenon, raden (noble gases), hydrogen, nitrogen, oxygen, fluorine, chlorine
Name some chemical properties (can be observed when a substance undergoes a chemical reaction to form a new compound)
reactivity
What is the flame test?
Flame tests are used to identify a certain cation through their distinctive colours as heat transitions the excited atoms to a higher energy level.
lithium = red
sodium = yellow-orange
potassium = purple
calcium = brick-red
barium = apple green
strontium = red
copper = blue green
Definition: Isotopes
the same element with a different number of neutrons but same number of protons. they usually give off radioactive decay
Definition: relative atomic mass
is the ratio of the weighted average of all natural isotopes of an element to one unit
= (mass of isotope 1 x % of frequency) + (mass of isotope 2 x % of frequency)
What is the empirical formula?
simplest ratio between different atoms
How to the lewis diagram for an draw ionic compounds?
using brackets + charges + showing full valency
How to draw the lewis diagram for covalent compounds?
showing bonds between as pairs electrons + showing valence electrons (both using dots or crosses)
- 2BG + 0LP - linear
- 3BG + 0LP - trigonal planar
- 2BG + 1LP - trigonal planar
- 4BG + 0LP - tetrahedral
- 3BG + 1LP - tetrahedral
- 2BG + 2LP - tetrahedral
- 5BG + 0LP - trigonal bipyramidal
- 6BP + 0LP - octahedral
- linear
- trigonal planar
- bent
- tetrahedral
- trigonal pyramidal
- bent
- trigonal bipyramidal
- octahedral
What are ionic networks?
a 3D lattice consist of cations and anions that are bonded by electrostatic attraction
- hard, brittle, high melting/boiling
- can only conduct electricity in aqueous form
What are covalent networks?
are extensive networks/chains of atoms bonded by strong covalent bonds
- very hard, brittle, high melting/boiling
- not electrical conductors
What are metallic structures? (metals)
are 3D lattices of metal cations in a sea of delocalised valence electrons
- hard (softer than other networks), flexible, high melting/boiling, lustrous
- conduct electrivity
What are covalent molecular structures?
are composed of discrete covalent molecules with no chemical bonds between them, but held by weaker intermolecular forces
- soft, flexible OR brittle, low boiling/melting
- do not conduct electricity
What is the absorption spectrum?
is produced when white light is passed through an element which absorbs specific wavelengths of light and leaves dark lines on a coloured spectrum
What is the emission spectrum?
is produced when an element is heated and electrons excite and de-excite producing coloured lines on a dark spectrum
What is rutherford’s model of the atom?
What is bohr’s model of the atom?
What is schrodinger’s model of the atom?
What is Effective Nuclear Charge? (ENC)
Z(eff) = no. of protons - shielding electrons (no. of electrons blocking the chosen electron, therefore total electrons - it’s current shell’s no. of electrons)
What is the ENC’s trend?
Across a period: increases
Down a group: decreases
What is electronegativity?
What is 1st ionisation energy?
the ability for the nucleus to attract a pair of electrons
the energy needed to remove a valence electron
What is the electronegativity and 1st ionisation energy trend?
across a period: increases
down a group: decreases
What are the reactivity trends?
group 1-2 metals: more reactive down the group
group 7: mildy reactive and increase down the group
Ionic bonds are created between ____
elements with a large difference in electronegativity (>1.8)(metals and non metals)
Polar (electrons are slighty tilted towards the more electronegative element - dipole moment) covalent bonds are created between ____
elements with a moderate difference in electronegativity (0.4-1.8)
e.g OH, HF, NH, SO, CCl
Non-polar covalent bonds are created between ___
elements with a small/no difference in electronegativity (<0.4)
What are allotropes?
are different structures of the same element in the same state although with different physical properties (e.g carbon, oxygen, boron, iron)
What are the 3 carbon allotropes?
- graphite (layers of covalent networks bonded ontop of each other using intermolecular forces)
- diamond (complex covalent network, each carbon atom is bonded to 4 others with no lone pairs)
- buckminsterfullerene (covalent molecular structure, a large ball of 60 carbon atoms covalent bonded together and then bonded to other balls using intermolecular forces)
Polarity of molecules depends on ___
- polarity of bonds (if there are no polar bonds the whole molecule is non-polar)
- molecular geometry (make sure that the charges don’t cancel each other out)
What are the 3 types of intermolecular forces? weakest to strongest.
- dispersion forces (electrons randomly moving around to cause a temporary dipole moment)(exists between ANY molecules)
- dipole-dipole forces (have a net dipole slightly + or - and force grows stronger with larger difference in electronegativity)(exist between POLAR molecules)
- hydrogen bonding (directly to the highly electronegative atoms and because hydrogen is so small, it can squeeze in)(between F, O, N and H)
Definition: Kinetic particle theory
a theory that states that all matter is composed of particles in motion and that the rate of motion varies directly with the temperature.
Oxidation/reduction reaction (metals, think abt the transfer of electrons)
half reactions in a reaction
OXIDATION: increases the charge of the element in the product from the reactant
REDUCTION: decreases the charge of the element in the product from the reactant
e.g Mg+O2=MgO (magnesium oxidised from 0 to +2)(oxygen reduced from 0 to -2)
metal + water = ____
metal hydroxide + hydrogen gas
(break into equation into ions and decide which element is oxidised and which is reduced)
acid + metal carbonate = ___
salt + water + CO2
(neutralisation) acid + base = ___
salt + water
NAG SAG (always soluble)
nitrates
acetates
group 1
sulfates
ammonium
group 7
EXCEPTION: SILVER, LEAD AND MERCURY (always insoluble)
