The Early Periodic Table
- The Periodic Table of the elements developed as a attempt to classify the elements.
- Not all elements were known at the time
- Mendeleev's table (founder of the modern periodic table) took account of unknown elements that were yet to be discovered and provided the basis for the modern periodic tale.
NB: Remember Dimitri Mendeleev the founder of the modern periodic Table
The Modern Periodic Table
- Mendeleev's Periodic Table was accepted by the scientific community because it showed pattern in the elements which were recognised.
- The modern periodic table is split up into groups e.g. Group 7 are the Halodides.
- The group that an element is in is determined by it's atomic number which is the number of Protons the element has.
- The number of electrons on the outer shell (energy level) determines it's chemical properties.
Note: All elements have similar Chemical properties because have the same number of electrons on their outer shells (outer energy shell)
- We can explain thrends in reactivity as we go down a group in terms of the number of energy levels in the atoms.
The Alkali Metals
Located In Group 1 of the Periodic table:- Li, Na, K, Rb, Cs, Fr (Symbols)
- All very reactive (stored in oil to stop them from reacting with Oxygen in air )
- Their Reactivity increases as we move down the group making Francium (Fr) most reactive
Although Lithium (Li) is the least reactive in the group, it's still very reactive.
- All Alkali metals have a very low density for metals.
- They are all very soft metals and can be cut "Like cheese" but the still have the very shiny silvery look of metals, however they tarnish in colour quickly as they react with oxygen.
- They have low boiling and melting points.
- They all have one electron on the outer shell (making them really reactive)
- They react with non-metals losing their single outer electron.
- When reacted with water you see Fizzing.
Found in Group 7 of the periodic table:- F, Cl, Br, I,, At (Symbols)
- They are all poisonous non-metals which have coloured vapours
- They have low melting and boiling points.
- They are poor conductors of heat and electricity.
- The reactivty decreases as you go down the group making F (Flourine) the most reactive.
- They exsist as diatomic molecules.
- They form covalent compounds by sharing electrons with other non-metal
- All form ions with a single negetive charge.
Bromine- Orangy Brown ; Iodine- Violot Vapour; Chlorine-Green; Flourine- Pale Yellow
We can use a more reactive Halogens to displace a less reactive Halogen from solutions of their salts
The Transition Metals
Found in the centre of the periodic table.
- Typical metalic structure
- Very good conductors of heat and electricity
- They are hard, tough and strong but can be bent or hammered into useful shapes.
- With the exception of Mercury which is a liquid at room tempreture, the transition metals have very high boiling and melting points.
- They have high densities.
- Not very reactive making them handy in everyday use. They do not react vigourously with Water or Oxygen.
- They can be mixed together to form alloys making them even stronger.
Acids and Alkali's
Acids- A substance that produced H+ (Hydrogen ions) whe dissolved in water.
Alkali- A soluble base which poduces OH- ions when dissolved in water.
ACIDS are PROTON DONERS
ALKALI (BASE) is a PROTON ACCEPTOR (Its was Brønsted and Lowry who came up with this theory and they were accepted because the theory was built on the foundation of Arrhenuis's Theories)
- We can classify acids and alkalis as 'strong' or 'weak' on the extent in which they ionise in water e.g. a strong acid or alkali is one that has is 100% ionised in water
- Ways to tell if a acid is strong or weak is 1. Where it comes on a pH scale
2. Observing the rate of reaction when a reactive metal is added to the acid.
Titration is used to measure accuratly how much alkali is needed to react completely with aknown ammount of acid or vice versa.
A suitable indicator should be chosen to show the end point of an acid-base reaction.
(Joke ALERT: What did one titration say to the other? Let's meet at the end-point... *tumble weed* :| ) Sorry people theres not much on titration so I'll make it a little interesting XD
(Note the maker of your cards is a strange person XD)
Formula for Titration: Moles= Concentration x Volume ( M= CV) you can arrange to to what you need.
Step 1- Calculate the moles of the substance you have the most sufficient data on by using the formula above (That means the substance which you have both the Concentration and Volume)
Using: moles= concentration x volume
Step 2- Write down the number of moles for the substance for which you have been asked to find the concentration for looking at the ratio.
Step 3- Satisfy the examiner by calculating the concentration of the substance you have been asked for.
Using: concentration= moles/ volume
Note: You need to be able to rearrange the formula to what the examiner wants.
Hard water- water containing dissolved calcium and/ or magnesium salts.
- The calcuim and/ or magnesium reacts with soap producing precipitate called scum.
- These salts decompose when heated and form Limescale.
Advantages of Hard Water
- May have health benifits to Humans. As calcium in water would help with the development of bones and teeth.
- some evidence suggests hard water helps to reduce the incidence of heart disease in people.
Disadvatages to Hard Water
- More expensive as it's difficult to produce a lather
- Difficult to wash with making scum instead of bubbles.
- Soft water does not contain salts that produce scum or scale, Hard water can be softened by removing those salts that produce scum and scale
1. Using washing soda which is added to hard wather and it participates out the magnesium and calcium ions into insoluble carbonates
2. Using a ion-exchange column, which contain sodium ions which are exchanged for the calcium and magnesium ions.
Water for drinking should contain low levels of dissolved substances and microorganisims
- Water is made fit to drink by:
Reservior ----> Filter-----> adding chlorine
Filtering to remove the solids and addind chlorine to kill bacteria
Pure water an be made by distillation
Used for some of the metals in Group 1 and 2
Lithium- Bright Red
Sodium- Golden Yellow
Calcium- Brick Red
Test for Negetive Ions
Test for Copper Carbonate: heat till it decomposes + result turns green to black
Test for Zinc Carbonate: heat + result turns from white to yellow
Test for sulphate ions SO4 -2 : Add dilluted hydrochloric acid follwed by barium chloride solution + Result a white participate is formed
Test for Nitrate Ions No3 : Add sodium hydroxide solution to substance followed by alluminium powder + result Alluminium reduces the nitrate ions and amonia gas is formed NH3, turns damp red litmus paper blue.
Metal ions form coloured precipitates with sodium hydroxide
- Copper III- light blue precipitate
- Iron II- dirty green precipitate
- Iron III- reddish-brown precipitate
Test For Halodides
Add Dilute nitric acid and silver nitrate solution to the unknown solution:
- Chlorine ions (Cl-) = White Percipitate
- Bromine ions (Br-)= cream percipitate
- Iodine ions (I-) = Pale yellow precipitate