- The periodic Table is the arrangement of elements in a table according to their atomic number. The elements are organized into groups (vertical rows) and columns (horizontal rows).- The groups are generally chemically similar.- Elements are classified as metals or non-metals. They are generally defined by electrical conductivity and their acid/base characteristics (Metal Oxides are Basic, Non-Metal Oxides are Acidic)- <1/4 of all elements are non-metals- Chemical behavior is determined by the amount of electrons in the outer shell of the element.- Group 1 and Group 7 elements tend to be the most reactive elements in the periodic table. - Group 0 elements tend to be the least reactive elements on the periodic table - In the centre of the periodic table there is a block of metallic elements, known as the transition metals.
The Alkaline Metals
- The Alkaline Metals are found in Group 1 of the Periodic Table and are metals (duh!)- They tend to have a low density (Li, Na and K float) - They tend to react with non-metals to form ionic compounds by losing an electron, gaining a noble gas electronic configuration, and thus forming a 1+ cation. - The compounds of Group 1 elements tend to be white solids and dissolve in water. - They react with water to form hydroxide salts and hydrogen. - They form soluble oxides and hydroxides to give alkaline solutions. - When Li, Na or K are placed in cold water the metal will react and melt, moving around the surface of the water. - Caesium is the most reactive, and as you go up the group the reactivity goes down with Lithium being the least reactive. - Density increases the further down the group you go. - As you go up the group the melting/boiling points increase, with Caesium melting/boiling at 28 and 671 C respectively and Lithium melting/boiling at 181 and 1342 C respectively.- They are found naturally as giant metallically bonded molecules.
The Transition Metals
- The transition Metals are typically metallic (duh!)- They are good conductors of heat, electricity, are strong and malleable, and have high densities. - They tend to have very high melting points, with the exception of Mercury (Hg)- They are far less reactive than the metals in Group 1+2, and react far less rapidly with water and air.- They generally lack reactivity, and are important in everyday life. - The majority of the transition metals form coloured compounds.- Examples of uses include: the use of iron in ammonia production; the use of Vanadium Oxide in the manufacture of Sulphuric Acid and the use of Manganese Oxide in the decomposition process of Hydrogen Peroxide.- They are found naturally as giant metallically bonded molecules.
- The Halogens are found in Group 7 of the Periodic Table.- They are all brittle and crumble as solids.- They form poisonous and pungent vapours.- As you go down the group they get darker.- They all have relatively low boiling and melting points; as you go up the group the lower the mp and bp get. - Bromine at room temperature is a liquid and Iodine is a solid; however they are volatile and form vapours at relatively low temperatures.- Iodine sublimes to form a purple vapour and is a dark-grey solid, Bromine is a brown liquid and boils to form a red-brown vapour. Chlorine is a green gas and flourine is a pale yellow gas. - They can react with metals to form ionic compunds by gaining an electron to become a 1- anion.- They all have 7 electrons in their outer shell.- They can undergo displacement reactions where a more reactive halogen will displace a less reactive one.- They can undergo reactions with Hydrogen but as you go down the group higher temperatures are required for it to take place. - They exist as diatomic molecules covelantly bonded together in nature.
- Redox Reactions, Displacement Reactions, Reduction Oxidization Reactions or whatever you want to call them are when a more reactive element takes the place of another, less reactive element, in a compound. The element which gains electrons is reduced, and the element which loses electrons is oxidized. - An example of a redox reaction is as follows: 2K-Cl + F2 → 2K-F + Cl2- In this example Flourine replaces Chlorine in the element; Flourine loses an electron in the process so is the oxidizing agent and is reduced , and Chlorine gains an electron so is the reducing agent and is oxidized.- To determine the oxidizer/reduced and the reducer/oxidized we use the Mnemonic OILRIG.- Oxidation Is Loss, Reduction is Gain. Hence the Flourine gains an electrons so is the oxidizing agent and is reduced, and Chlorine loses an electrons so is the reducing agent and is oxidized.- Flourine effectively steals the electron from Chlorine and as a result of its new negative charge it bonds with the Potassium.
- The Noble Gases are found in Group 0 or 8 of the Periodic Table. - They are all colourless and odourless gases which have a full outer shell of electrons. - They all exists as monoatomic structures and are chemically unreactive/cannot form bonds (under most circumstances...)- The boiling and melting points go down as the group ascends; this trend is the same for the density. - Helium is used in airships and balloons as it is less dense than air yet unreactive unlike Hydrogen Gas.- Neon is used for lights as when an electrical current is passed through it the Neon gives out a bright light.- Argon is used in lightbulbs as it provides an inert atmosphere which stops the heated tungsten filament from reacting with the air.- Krypton is used in medicine for lasers.- Xenon is used in headlights and flashlights.- Radon is given off when there is an earthquake imminent ; and thus provides warning.
The Noble Gases
The Composition of the Atmosphere
- Dry air is composed of three main gases; Nitrogen, Oxygen and Argon. It also contains trace amounts of Xenon, Neon, Hydrogen, Helium, Krypton and Carbon Dioxide.- In general, dry air is 78.8% Nitrogen, 20.95% Oxygen, 0.93% Argon and <0.05% Xenon, Neon, Hydrogen, Helium, Krypton and Carbon Dioxide.- Because Copper only reacts with Oxygen of all of the air's gases, you can prove that there is 21% Oxygen in the air by: Heating some copper, and then (between two syringes) passing air past it again and again until the volume reading of air is constant. Then you leave it to cool, subtract the lost volume of air and that volume is the volume of Oxygen. From this you can find the proportion of Oxygen in the air by dividing the lost volume over the original volume and multiplying by 100 to get a percentage.
- To do this Hydrogen Peroxide (H2-02) and Manganese Dioxide (Mn-02) are required.- The manganese Dioxide is a catalysts which speeds up the decomposition of the H2-02.- The balanced chemical equation is as follows: 2H2-02 → 2H2-O + O2- To test for the O2 you must carry out the glowing splint test.
- Carbon Dioxide is Colourless and Odourless.- It is more dense than air. (Fire extinguisher)- It is soluble in water. (Fizzy Drinks)- It is solid below -78 C (Dry Ice)- It can be produced in three ways: Acid Base Neutralization: Ca-C-O3 + 2H-Cl → C-O2 + H2-O + Ca-Cl2Thermal Decomposition: Ca-C-O3 + Heat → C-O2 + Ca-O Cu-C-O3 + Heat → C-O2 + Cu-O- It reacts with water to form Carbonic Acid: C-O2 + H2-O → H2-C-O3 (Rainwater is acidic because of this)-It reacts with alkalies to form carbonates: C-O2 + 2Na-O-H → Na2-C-O3 + H2-O C-O2 + Ca-(O-H)2 → Ca-C-O3 + H2 - O