C2 the periodic table

2.1

• first periodic table was sorted by atomic weight
• Mendeleev’s table left space for undiscovered elements, his theory ended up right

2.2

• chemicals in the same group tend to have similar chemical properties because they have the same number or electrons on the outer shell
• noble gases have a full outer shell meaning they are stable and unreactive.

2.3 group 1

• alkaline metals are very reactive and have to be stored in oil because they would react with oxygen or water
• they are called alkaline metals because their pH is so high

2.4 group 7

• halogens have a low melting and boiling point because their intermolecular forces of attraction are weak
• a more reactive halogen can displace a less reactive one in a reaction

2.5

• the bigger the atom (more electrons), the more the outer shell is ‘shielded’ from the nucleus. Therefore it is more reactive
• sodium’s outer shell is much more shielded than lithium’s because lithium has less electrons/shells

2.6

• transition elements are found in the central block of the periodic table
• they are denser, stronger and harder than group 1 metals