The Periodic Table

• The modern Periodic Table is ordered by atomic number.
• The early lists of elements were ordered by atomic mass.
• Mendeleev swapped the order of some elements to group them by their chemical properties.
• Mendeleev left gaps in his periodic table to leave room for elements that had not been discovered yet.
• Elements in the same group have similar chemical properties because they have the same number of electrons in their outer shell.
• Metals are to the left of the Periodic Table.

  Non-metals are to the right of the Periodic Table.
• Group 1 elements are also called the alkali metals.
• Alkali metals are elements that react with water to form an alkali.
• General reactions of alkali metals:

  Metal + Oxygen -> Metal oxide

  Metal + Chlorine -> Metal chloride

  Metal + Water -> Metal hydroxide + Hydrogen
• Reactivity of alkali metals increases down the group because the atoms become larger so the outermost electron is further from the nucleus, meaning there are weaker forces of electrostatic attraction and more shielding between the nucleus and outer electron and it is easier to lose the electron.
• Group 7 elements are also called halogens.
• The first four halogens are: F2, Cl2, BR2, I2
• The melting points of halogens increase down the group.
• The melting points of halogens increase down the group.
• Reactivity of halogens decreases down the group because the atoms become larger so the outermost shell is further from the nucleus, meaning there are weaker forces of electrostatic attraction and more shielding between the nucleus and outer shell and it is easier to gain an electron.
• A displacement reaction is when a more reactive element takes the place of a less reactive element in a compound.
• Group 0 elements are also called noble gases.
• Noble gases are inert because they have full outer shells so do not need to lose or gain electrons.
• Melting points of noble gases increase down the group.