Reactivity of metals

Metallic behaviour

• Metallic elements are found on the left-hand side of the periodic table

  • Metallic atoms tend to be larger than non-metals in the same period

  • Metallic atoms have a lower effective nuclear charge (core charge) 

• This means that atoms tend to lose their outer shell electrons

  • Atoms which lose electrons are no longer neutral

  • They form positive ions, called cations

Predicting charges of cations

• The cation charge of metals can be determined by losing electrons until the shells have a stable noble gas electronic configuration
  (i.e 8 valence electrons/full p orbital)

Group 1 metals form +1 cations, lose one electron

Group 2 metals form +2 cations, lose two electrons

Group 13 metals form +3 cations, lose three electrons

Examples:

Write the electronic configuration of the atoms below and hence determine the charge of the ion. (you may choose to use the shell or subshell model)

a) Calcium b) Aluminium

1s2, 2s2, 2p6, 3s2, 3p6, 4s2 1s2, 2s2. 2p6, 3s2, 3p1
charge of ion: +2 charge of ion: +3

Reactivity of metals

Although metals all tend to lose electrons, they way in which metals can lose electrons can vary significantly between metals.

Reactivity refers to how easily an atom or element undergoes a chemical reaction, often by losing, gaining, or sharing electrons to form a stable configuration.

• Atoms which are unreactive are described as inert

Reactions with water, oxygen and acids

Reactivity depends on not just the metal but also what it is reacting with

• We often react with water, oxygen and acids as these are commonly found in environments or in laboratory conditions

• Metals which react with water typically form H₂ and metal hydroxides

• Oxygen is very good at taking electrons and often reacts with metals to form their metal oxides  (this process is known as oxidation)

• Acids which react with metals will corrode the metal and produce hydrogen gas and metal salts

Reactivity series

Chemists have used experimental data to produce a reactivity series of metals

In general, the more loosely-bound valence electrons
are to the nucleus, the more reactive the metal

Going down group:

reactivity increases

Because... atomic radius increases, valence electrons are further from nucleus, therefore more reactive

Going across period:

reactivity decreases

Because...atomic radius decreases, valence electrons are closer to the nucleus, therfore less reactive

Explain why metals such as iron, copper, titanitum and aluminium must be mined in their oxide forms (ores) but metals such as gold and platinum can be found naturally on earth in their elemental forms?

Metals like iron, copper, titanium, and aluminium must be mined as oxides (ores) because they are highly reactive and readily combine with oxygen and other elements in the Earth's crust. In contrast, gold and platinum are found in their elemental forms because they are very unreactive.