Chemistry unit three (part one)
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- Created on: 29-03-14 10:12
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- Chemistry unit three (part one)
- The periodic table
- The modern periodic table
- The atomic (proton) number of an element determines its position
- The number of electrons in the outer shell determines the chemical properties
- The group number equals the number of electrons in the outer shell
- The distance between the outer electrons and the nucleus and the number of occupied shells can help explain trends of reactivitiy
- The early periodic table
- The periodic table of elements was created to classify the elements. It arranges them into a pattern in which similar elements are grouped together
- Newlands' table put elements in order of atomic weight but failed to account for unknown elements
- Mendeleev's table left gaps for unknown elements and so provided the basis for the modern periodic table
- The modern periodic table
- Groups
- Group 1 (alkali metals)
- They react readily with air and water.
- They all react with water to produce hydrogen and an alkaline solution containing the metal hydroxide
- They form positive ions with a 1+ charge in reactions to make ionic compounds.
- Their compounds are usually white or colourless crystals that dissolve in water to produce a colourless solution
- Their reactivity increases going down the group
- The transition elements
- Compared with the alkali metals they have a much higher melting point and higher densities. They are also harder and stronger and less reactive
- Don't react vigorously with oxygen or water
- Can form ions with different charges and in compounds that are often coloured
- Are important industrial catalysts
- Group 7 (halogens)
- Non-metallic elements. They exist as small molecules made up of pairs of atoms.
- They have low melting and boiling points that increase going down the group.
- At room temperature fluorine is a pale yellow gas, chlorine a green gas, bromine a red-brown liquid and iodine a grey solid. Iodine easily vaporises to a violet gas
- Have seven electrons in their outer shell so when they form ionic compounds with metals, their halide ions have a 1- charge.
- Form covalent bonds by sharing electrons
- A more reactive halogen can displace a less reactive halogen to form a solution of one of its salts
- The reactivity decreases going down the group
- Group 1 (alkali metals)
- The periodic table
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