The Alkali metals
- The elements of group 1 of the periodic table are called the alkali metals
- The metals all react with water to produce hydrogenn and an alkaline solution containing the metal hydroxide
- The reactivity of the alkali metals increases as we go down the group
- The halogens exist as diatomic molecules
- They have low melting points
- they are poor conductors of heat and electricity
- The halogens all form ions with a negative charge
- The halogens form covalent compounds by sharing electrons with other non-metals
- The reactivity of the halogens decreases going down the group
The Transition elements
- Nearly all the transition elements have high melting points and high densities
- The transition metals are strong and hard, and are good conductors of heat and electricity
- The transition metals do not react vigorously with oxygen or water
Reactive metals: react vigourously with other elements like oxygen or chlorine and with water. They are all soft- some can even be cut with a knife like cheese!
Transition metals: Contain elements than most people think of when they hear the word "metal". These metals are not really reactive. Some like gold and silver are so unreactive they are called noble metals.
Non-metals: Have low melting and boiling points and many are liquids or gases at room temperature and pressure.
Noble gases: These non metal elements are very unreactive and its very difficult to get them to combine with other elements.
The early periodic table
- John Dalton is a teacher from manchester, he arranged the elements in order of mass measured in various chemical reactions. In 1808 he published a table of elements in his book.
- 1863 John Newlands built on Daltons idea with his law of octaves. He based his idea on the observation that every eighth element seemed similar. He was so determinedf to make it work he made vital mistakes. He didnt leave spaces for new elements and he put them in his octave order even though some didnt even fit in.
- 1869 Russian scientist Dmitri Mendeleev arranged the elements in a table in order of their atomic masses, he arranged them so their physical and chemical properties could be seen. He even left gaps for new elements. He is remembered as the father of the modern periodic table.
Strong and weak acids/alkalis
- Acids in aqueous solutions produce H+ ions.
- Alkalis in aqueous solutions produce OH- ions.
- A strong acid or base is 100% ionised in water
- A weak acid or alkali is only partly ionised in water
- An acid is a proton donor.
- A base is a proton acceptor.
- Titration is used to measure accuratly how much slksli is needed to react completely with a known amount of acid (or vice versa)
- The poin of which an acid-base reaction is complete is called the end point of the reaction
- A suitable indicator should be chosen to show the end point of an acid-base reaction
- Pipette measures out fixed volume of solution
- Burette measured the volume of solution added.
- To calculate the concentration of a solution
1. Calculate the mass in grams of solute in 1cm3 of solution.
2. Calculate the mass in grams of solute in 1000cm3 of solution - convert the mass on grams to moles