METALS
All the elements can be classified into two main groups: metals and non-metals.
Each has some common properties within the group. Metals exhibit metallic properties and non-metals exhibit non-metallic properties.
All the elements in the 1st group (except hydrogen), 2nd group and 3rd group (except boron) are metals. In addition to these transition and the inner transition elements are also metals.
From the 4th and 5th group of the periodic table, tin, lead and bismuth are metals as well.
Some elements in the periodic table between metals and non-metals show some metallic and non-metallic properties. These are called metalloids.
Atomic structure of metals: Metals have low number of electrons in their valance shell. So, they tend to give these electrons in their compounds. Their atomic radii are larger than those of non-metals.
The force that holds the metals atoms together is called metallic bond. Metallic bonding is explained by electron sea model. According to this model, positively charged metal ions are found in an electron sea that is formed by the
valence electrons of the metals.
Physical Properties of Metals
- All the metals are in solid state except mercury.
- All the metals have metallic shiny color. For example gold is yellow, copper is red, aluminum is white and iron is silvery gray.
- The valence electrons of metals are mobile so, they conduct electricity.
- The melting points of metals change widely. For example melting point of tungsten (W) is highest and equal to 3380 o C. But the melting point of mercury is –39 oC.
- Most metals are hard. Chromium and tungsten are the hardest metals and the alkali metals are the softest ones.
- They are not soluble in water but when they are melted one metal can be dissolved in another metal. These types of metal mixtures are called alloys.
- Metals are ductile. They can be drawn into wires.
- Metals are malleable. They can be hammered into sheets.
Chemical Properties of Metals
Activity order of metals:
Li-K-Ba-Ca-Na-Mg-Al-Mn-Zn-Fe-N-Sn-Pb-H2-Cu-Hg-Ag-Pt-Au
MORE ACTIVE à LESS ACTIVE
1. Reaction with water:
Active metal + water à base + hydrogen gas
2Na + 2H2O à 2NaOH + H2
Metals less active than zinc give metal oxide:
Zn + H2O à ZnO + H2
2. Reaction with acids:
Metals (except inert ones) + acids à salt + hydrogen gas
Mg + 2HCl à MgCl2 + H2
3. Reaction with salts:
Metals can react with the salts of less active metals.
Zn + CuCl2 à ZnCl2 + Cu
4. Reactions with nonmetals:
2Al + 3Br2 à 2AlBr3