What are the patterns in the properties of elements?
- Created by: vaibhi.dua
- Created on: 21-03-15 14:33
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- Chemical patterns
- Element
- Relative atomic mass
- Minus the proton number equals the neutron number
- Proton number
- Is also the electron number
- Defines the element
- Relative atomic mass
- Periodic Table
- Elements are arranged in order of proton number
- This gives a repeating pattern of their properties
- Each element is placed beneath those with similar properties
- This gives a repeating pattern of their properties
- Attempts were made to order the elements
- Their actual masses could not be measured so they were compared to the mass or hydrogen
- This is called RELATIVE ATOMIC MASS
- Their actual masses could not be measured so they were compared to the mass or hydrogen
- Döbereiner proposed the 'law of Triads'
- Three elements with similar properties
- The relative atomic mass of the middle element was close to the average of the other two
- Three elements with similar properties
- Newlands arranged the elements in order of their atomic mass.
- Proposed the 'law of Octaves'
- Every eight element had similar properties
- Didn't work for all elements so theory dismissed
- Every eight element had similar properties
- Proposed the 'law of Octaves'
- Mendeleev put the elements in order of relative atomic mass and left gaps for unknown elements
- He predicted what the properties of the undiscovered elements would have
- Arranged it so that groups of elements with similar properties fell into vertical columns
- Period
- A row of elements, the row number tells you how many shells the atom will have
- Column
- Each column contains a group of elements with similar properties
- The Group number tells you the amount of electrons in the outer shell
- Each column contains a group of elements with similar properties
- Metals and Non-metals
- Metals on the left, non-metals on the right
- Because there are patterns in the way the elements are arranged you can predict properties of elements
- Elements are arranged in order of proton number
- Alkali Metals
- Li (Lithium)
- Na (Sodium)
- K (Potassium)
- Shiny when freshly cut but tarnish rapidly ( they react with the oxygen)
- Soft metals
- Increased reactivity as you go down the group
- Melting points and Boiling points decrease as you go down the group
- The densities generally increase as you go down the group
- All have similar formulaes of compounds
- Reactions with cold water:
- 2 Li + 2 H2O -> 2LiOH + H2
- Produce strong alkaline solution and hydrogen gas
- Fizzes steadily until it disappears
- 2 Na + 2 H2O -> 2NaOH + H2
- Produce strong alkaline solution and hydrogen gas
- Fizzes quickly along the surface of the water. Burns with an orange flame
- 2 K + 2 H2O -> 2KOH + H2
- Sets on fire with a lilac flame. Fizzes around vigorously.
- 2 Li + 2 H2O -> 2LiOH + H2
- Reactions with chlorine:
- 2 Li + Cl2 -> 2LiCl
- Produce colourless, crystalline salts
- White powder settles in jar
- 2 Na + Cl2 -> 2NaCl
- Produce colourless, crystalline salts
- Burns with a yellow flame. Clouds of white powder is made
- 2 K + Cl2 -> 2KCl
- Reacts more violently than Sodium!
- 2 Li + Cl2 -> 2LiCl
- Because they are so reactive you must wear goggles and gloves. They will react with the water in your sweat!
- Hazardous symbols
- Explosive
- Enough stored energy in them to explode
- Illegal to carry out unauthorised experiments
- Enough stored energy in them to explode
- Toxic
- Poisonous chemicals
- Wear goggles, gloves, mask and use in fume cupboard
- Poisonous chemicals
- Corrosive
- Concentrated solutions of strong acids and strong alkalis
- Wear goggles and gloves
- Concentrated solutions of strong acids and strong alkalis
- Oxidizing
- They provide oxygen to substances that are flammable
- Wear eye protection and keep away from flammable things
- They provide oxygen to substances that are flammable
- Highly flammable
- Chemicals that ignite very easily
- Wear eye protection. Keep away from flames and sparks and also from oxidising agents.
- Chemicals that ignite very easily
- Explosive
- Halogens
- Cl2 (Chlorine)
- Gas at room temperature
- Yellow green
- Br2 (Bromine)
- Liquid at room temperature
- Red-Brown
- I2 (Iodine)
- Solid at room temperature
- Shiny purple crystals. Dark purple gas
- Diatomic molecules
- Melting and boiling points increase as you go down the group
- The have similar formulas of compounds
- The reactivity goes down as you go down the group
- Chlorine reacts very vigorously with sodium. Iodine reacts very slowly with sodium
- Can be shown by displacement reactions
- Chlorine is more reactive than Bromine so it will displace the Bromine. The solution turns brown because because of the displaced Bromine
- Cl2 + 2NaBr -> 2NaCl + Br2
- A more reactive halogen will displace a less reactive halogen from a solution of one of its salts
- Chlorine is more reactive than Bromine so it will displace the Bromine. The solution turns brown because because of the displaced Bromine
- Because they are so reactive you must use a fume cupboard, gloves and goggles
- Cl2 (Chlorine)
- Formulaes
- H2 (Hydrogen)
- H2O (Water)
- Cl2 (Chlorine)
- Br2 (Bromine)
- I2 (Iodine)
- LiCl (Lithium chloride)
- NaBr (Sodium bromide)
- KI (Potassium iodide)
- Element
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