Periodic Table And Energy Flashcards
(34 cards)
Periodic table then
Mendeleev arranged elements in order of atomic mass
-also lined up elements with similar properties
-left gaps assuming some were yet to be discovered
Trends across a period
same number of shells
- different number of electrons in outer shell
Trends down a group
Same number of electrons in outer shell
-number of shells increase (shielding)
-atomic radius increases
Ionisation energy
how easily an atom loses electrons to form positive ions
-atomic radius increases i energy decreases
-nuclear charge increases I energy increases
-electron shielding increases i energy decreases
Successive ionisation energies
He(g) —> He+(g) + e-
He+(g) —> He2+(g) + e-
Second ionisation energy
energy required to remove one electron from each ion in 1 mole of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions
1st ionisation trends
across period- (increases)
nuclear charge increases⬆️
nuclear attraction increases⬆️
atomic radius decreases🔻
Down group- (decreases)
atomic radius increases
shielding ⬆️
nuclear attraction🔻
giant covalent structures
-insoluble in most solvents
-do not conduct electricity
(except graphene & graphite)
-high melting & boiling points
trends in melting point (period 2)
-Li –> C increases (giant structures)
-decreases dramatically to N as they are simple molecules so easier to overcome bonds
trends in melting point (period 3)
Na –> Si increases as they are giant structures and atomic charge increases
-decreases dramatically to P as it is now simple molecules
group 7 halogens
electronegativity decreases as you move down
-number shells increases
-weaker attraction
-BP increases as you move down
-more electrons and more induced dipoles (harder to break)
halogen colours
fluorine-pale yellow gas
chlorine- yellow green gas
bromine - dark red/brown liquid
iodine - grey black solid
astatine- very rare & radioactive solid
qualitative analysis of halide ions
-add nitric acid to get ride of carbonate ions
-then add silver nitrate
fluoride- no precipitate
chloride-white precipitate (dissolves in dilute NH3)
bromide-cream precipitate (dissolves in conc NH3)
iodide-pale yellow precipitate ( does not dissolve in either)
Qualitative analysis of sulphate ions
Sulfate ions
- dilute nitric acid (remove carbonate ions) + barium nitrate
white preciptate BaSO4 formed
qualitative analysis of carbonate ions
carbonate ions
-add dilute nitric acid; if bubbles form product could be carbonate
-check if CO2 bubble thru limewater (cloudy)
Enthalpy H
measurement of the heat energy in a chemical system
ethalpy change = H(products) - H(reactants)
endothermic reaction
heat into system from surroundings
system gains temp
-surroundings temp decreases
-bond breaking energy required
exothermic reaction
-bond making
heat transferred to surroundings from system
loses heat (temp drops)
-temp of surroundings increases
standard enthalpy change conditions
pressure= 100kpa
temp= 25 c
conc= 1moldm3
state=physical state normally
standard enthalpy change of reaction
enthalpy change that accompanies a reaction in the molar quantities shown in chemical equation under standard conditions
standard enthalpy of formation
enthalpy change that takes place when 1 mole of a compound is formed from its elements under standard conditions
1/2 O2 to make the product 1 mole only
standard enthalpy of combustion
the enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions
standard enthalpy change of neutralisation
the enthalpy change that accompanies the reaction of an acid and a base to form one mole of water under standard conditions
q=mc^T
q= energy change of surroundings
m= mass of surroundings
c= specific heat capacity (4.18kjg-1k-1)
^T= change in temp
if - = endothermic
if + = exothermic
q/n to see per mole of the reactant
opposite to answer +/- as now talking about reactant heat loss or gain
