atoms and molecules Flashcards
elements come in 3 states of matter
solids - metals
liquids - Hg & Br2
gases - diatomic and inert monoatomic
allotropes
element that has different structural forms / connected in different ways
atoms sub atomic particles
protons
electrons
neutrons
atomic number
number of protons + number of electrons
mass number
number of protons + number of neutrons
protons
are positive with one unit of weight
electrons
are negative and have practically no weight
neutrons
are neutral with one unit of weight
atomic number
total number of protons
noble gases
helium
neon
argon
krypton
xenon
noble gas
this has a complete outer electronic shell
isotopes
atoms having the same value of protons but different values for neutrons
anions
have a minus sign
cations
have a positive sign
pure substances
elements and compounds
uncombined natural sources
silver Ag, gold Au, nitrogen N2, sulfur S
oxides
chromite FeCr2O4, magnetite FeO4, water H2O, carbons dioxide CO2
carbonates
limestone CaCO3, dolomite CaCO3MgCO3
halides
salt NaCl, fluorite CaF2
sulfides
galena PbS, cinnabar HgS
phosphates
monazite La(PO4)
covalent bond
sharing electrons between atoms
ionic bonding
electrostatic attraction between oppositely chatted atoms
covalent molecule examples
chlorine, iodine, carbon dioxide, methane, sulfur
sublime
solid turning directly into vapour (iodine)
ionic bonding
a transfer of electrons to achieve a filled shell
ionic compound examples
NaCl sodium chloride, MgO magnesium oxide
cations
these are positively charged species formed when neutral atoms low electrons
anions
negatively charged species formed when a neutral atom gains electrons
common cations
H+ , K+ , Cu+ , Cu2+
common anions
Cl- , F- , S2-
what ionises to give cations
metals
what ionises to give anions
non-metals
complex anions
NO3 nitric acid
(CO3)2- carbonate
acids
HNO3 nitric acid
H2SO4 sulfuric acid
H3PO4 phosphoric acid
what are bases
proton acceptors
salts
formed by the replacement of the H+ ions of an acidic by another positive ion
reaction of acids with bases
HCL + NAOH -> NACL + H2O
H2SO4 + 2KOH -> K2SO4 + 2H2O
HN03 + NH3 -> NH4NO3
hydrogen bonding
the attraction between hydrogen atoms and either nitrogen, oxygen, or fluorine atoms
hydrogen bonding strength
they have about 10th the strength of an average covalent bond and are constantly broken and reformed in liquid water
how are salts formed
combining positive ions (cations) with negative ions (anions)
what is a mole
the amount of substance which contains as many objects, atoms, molecules or things as the number of atoms in 12g of C12
mass of an atom
in atomic mass units it is equal to the mass in grams of one mole of that element
what is the number of objects in 1 mole called?
the Avogadro Constant (equal to 6.022 x 10^23 mol^-1)
van der Waals forces
exist between non-polar molecules or atoms - weakest of all intermolecular forces