Periodicity Flashcards
Periodicity
Repeating patterns of chemical, properties reactions
Reactivity
S block :reactivity increases down the group
Non-metals -reactivity decreases down the group
Tms-fairly reactive
Lanthanides - similar reactivity - 3+ions
Actinides -radioactivie metals - only th and u occurred naturally in earths crust
Trends in period 3
Na mg al -metals giant structures ,lose outer electrons to form ionic compounds
Si-semi metal forms covalent bonds
P,s,cl -non metals ,accepts electrons to form ionic compounds or share electrons to form covalent
Ar-undeactive
Trend of group 2 metals in water
reactivity of Group 2 metals with water, is an increase down the group. The outer electrons are easier to remove as they are further from the nucleus and there is more shielding resulting in a lower nuclear attraction.
Define the bonding in magnesium
Metallic bonding . Forces of attraction between the sea of delocalised electrons and the positive cations metal atoms (mg2+)
Explain in terms of structure and binding why magnesium chloride has a high melting point
Giant ionic lattice between mg2+ and cl- ions strong electrostatic forces of attraction between them.
Group 2 alkaline earth metals
S block
Beryllium is not typical of the group so not considered
2 electrons in outer s orbital
Atomic radii increases down the group
Melting point decreases down the group
1st and 2nd ionisation energies decrease down the group
SULFATE solubility least to most
Baso4
Caso4
Mgso4
Use of baso4
Used in X-rays as barium meals
Barium would be toxic if it entered the blood stream but as it is insoluble it can not be dissolved and can be used as medical tracers
Hydroxide solubility least to most
Mg(oh)2
Ca(oh)2
Ba(oh)2
Use of mgoh2
Used as an indigestion tablet in o neutralised stomach acid-antacid
Use of (oh)2
Used in agriculture
Known as slaked lime
Used to neutralise acidic soils to encourage plant growth
Solubility trends
Singly dharged anions increase solubility down the group
Doubly charged anions decrease in solubility down the groups
Test for SULFATE ions
Add acidified bacl2 to solution containing SULFATE ions
Whir predicate formed baso4
Acidified with hcl to remove carbonates which also produce white prec
Barium SULFATE equation
Ba 2+ +so42- - > baso4
Uses of group 2 - titanium
-titanium is used in the aerospace industry and for replacement hips
-not easy to extract usually extract with carbon but this forms titanium carbide and makes the metal brittle
-so titanium oxide is first reacted with chlorine and carbon to from ticl4When meduced eith magnesium’s
Titanium reduced with magnesium
Ticl4 + 2mg —->2mgcl2 +ti
Calcium oxide and calcium carbonate
1)alkaline slurry -mix capo of caco3 with water
2)wet scrubbing - acidic so2 removed xfrom flue gasses by spraying with slurry
3)calcium sukfate produced
Group 7 physical properties
-non metals and don’t conduct electricity
-brittle and crumbly when solid
-poisonous and smells
Fluorine
Pale yellow
Chlorine
Green yellow gas
Bromine
Red brown liquid
Iodine
Blue black solid
Darker as you go down the group
Atomic radius in halogen
Increases from fluorine to chlorine as number of shells increase so outer shell electrons further away
More energy levels
Melting point and boiling point in halogen
They increase , number of electrons increase, ban Dee waal forces increases in strength so more energy needed to overcome them
Electro negativity in halogens
Electronegativity decreases from fluorine to iodine
Fluorine is the most electronegative
More energy levels occupied but nc increases
Ionisation energy
Decreases down the group
Greater radius more shielding
Fluorine anomaly
Small so leads to repulsion between lone electrons because tHey are close together
Oxidising ability in halogens
Good ability
Their oxidising power decreases down the group
Due to greater shielding and atomic radius
Displacement reactions
Halogens react with metal halodes in solutions
A more reactive halide will displace a less reactive one
Extracting group 7
Can extract bromine from sea water
Cl2+2br- =br2 +2cl-
Extracting iodine from kelp
2I- +mno2 +4h+ = mn2+ +2h2o +i2
Chlorine use
-chlorine reacts with cold water to produce chlorine ions and chloride ions
-cl2 +h2o = clo- +cl-+2n+
Both oxidise and reduced this is disproportionation
In the presence of uv light ,chlorine decomposes water to produce oxygen and hydrophobic acid and chlorine is reduced
Used in bleach also disproportionation
Chlorine reacts with cold dilute naoh to produce sodium hypochlorite
Halides as reducing agents
Halide ions are good reducing agents as they donate electrons to the species being reduced
Ability reduce increases Down the group
