8 Chemistry - Structure and Bonding
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What is an ion
An element or a molecule with an imbalance of change They are either positive or negative Formed between metals and non-metals
What has to happen to an ion to become an ion?
It gains or loses an electron
General properties of ionic compounds
High melting/boiling points (takes a lot of energy to break the bonds) Usually soluble in water (water molecules attract ions away) Conduct electricity when melted or dissolved (ions are charged and free to move)
What are the scientific names for gaining or losing electrons?
Gain: reduction Loss: oxidation Oxidation Is Loss Reduction Is Gain
What are positive ions called?
Cations they are usually metals (“pussytive”)
What are negative ions called?
Anions they are usually non-metals
When do covalent bonds occur?
When electrons are shared between non-metals
Describe the structure of graphite
Each carbon has a covalent bond with 3 other carbons, making rings which lie on top of each other (these slide over each other easily). It is able to carry a charge through a 4th electron free of bonds.
Describe the structure of diamond
Each carbon forms a covalent bond to 4 other carbons, these hold the structure in place making it very hard.
Properties of covalent compounds - Simple molecular compounds
Volatile Low melting/boiling pnts Insulators (dont conduct heat) Insoluble in water (generally)
Properties of covalent compounds - Giant covalent compounds (diamond, graphite, fluorine)
Not very volatile High melting/boiling pnts Insulators (except graphite) Insoluble in water
How do you prove water?
• Turns white anhydrous copper(III) sulphate blue • Turns blue cobalt chloride paper pink or -Boils at 100 °C, melts at 0°C
How is water treated?
(Know process diagram) Chlorine - kills bacteria Fluoride - helps fight tooth decay
What is the composition of air?
78% nitrogen 21% oxygen 1% other gases
How do I extract oxygen and nitrogen from the air?
Fractional distillation
What are common pollutants in the air?
Carbon dioxide CO2 Carbon monoxide CO Sulphur dioxide SO2 Nitrogen oxides NO and NO2 Lead compounds
What are the effects of pollutants?
Breathing problems Brain diseases Kills animals and plants Acid rain
What are catalytic converters and why are they important?
(Catalysts: help speed up reactions) Catalytic converters: convert poisonous gases from car engines into other gases.
What are catalytic converters made of?
Transition metals: platinum palladium rhodium
Equations in a catalytic converter
Reduced: 2NO (g) —> N2(g) + 02(g) nitrogen monoxide —> nitrogen + oxygen Oxidised: 2CO(g) + O2 —> 2CO2(g) carbon monoxide + oxygen —> carbon dioxide
Why does a catalytic converter have honeycomb shapes inside?
it increases surface area, increasing also the rate of reaction
what is the Haber process?what are the conditions?
It makes ammonia (NH3) Made in 450°C, 200 atmospheres N2(g) + 3H2(g) 2NH3(g)
What is Contact process? What are the conditions?
Makes sulphuric acid 450*C, less than 2 atmospheres S(s) + 02(g) —> SO2 (g)
What is needed for iron to rust? Equation?
water, iron, air 4Fe(s) + 3O2(g) + H2O(l) —>2Fe2O3.H2O(s) iron + oxygen + water —> hydrated iron (III) oxide (or rust)