the periodic table

• how was the modern periodic table ordered?

  atomic number
• how was the early lists of elements ordered?

  atomic mass
• why did Mendeleev swap the order of some elements?

  To group them by their chemical properties
• why did Mendeleev leave gaps in his periodic table?

  undiscovered elements.
• why do elements in a group have similar chemical properties

  same number of electrons in the outer shell
• what name is given to the group one elements?

  alkali metals
• why are the alkali metals name this?

  They are metals that react with water to form an alkali
• give the general equation for the reactions of alkali metals with oxygen

  Metal + oxygen ---> metal oxide
• give the general equation for the reactions of alkali metals with chlorine

  Metal + chlorine ---> metal chloride
• give the general equations for the reactions of alkaline metals with water

  Metal + water ---> metal hydroxide + hydrogen
• How does the reactivity of alkali metals change down the group?

  Increase
• why does the reactivity of the alkali metals increase down the group?

  They are large atoms of the outermost electron is further from the nucleus meaning there are weaker electrostatic forces of attraction and more shielding between the nucleus and outer electron so easier to lose the electron
• what is the name given to the group 7 elements?

  Halogens
• how did the melting point of the halogen change down the group?

  Increases
• how does the reactivity of the halogen changes down the group?

  Decreases
• why does the reactivity decrease down the group 7

  They are large atom so the outermost shell is further than the nucleus meaning that there are weaker electrostatic force of attraction and male shielding between a necklace and outer shell and it's harder to gain an electron
• what is a displacement reaction?

  When a more reactive element takes the place of a less reactive one in a compound
• what name is given to the group 0 elements?

  Noble gases
• why are the noble gases inert

  They have full outer shell so do not need to lose or gain electrons
• how did the melting point of the noble gases change down the group?

  Increase