Properties of elements in Group 1A, the alkali metals 

• The alkali metals are the elements Li, Na, K, Rb, Cs.
• These elements have relatively low melting points. Cesium melts at body temperature, 37^oCelsius.
• They are soft enough that they can be cut with a knife.
• They react violently with water.

Properties of elements in Group 2A, the alkaline earth metals 

• The alkali metals are the elements Be, Mg, Ca, Sr, Ba, Rd.
• These elements have higher melting points than the alkali metals.
• They are harder and tougher. Magnesium is used to fabricate car parts like wheels.
• Calcium reacts with water. Magnesium clearly doesn't react with water or else it couldn't be used in car parts.

Properties of elements in Group 7A, the halogens  

• The halogens, F, Cl, Br, I, At, are nonmetals.
• Halogens have lower melting points than the alkali metals. Fluorine and chlorine are gases at room temperature
• The halogens are corrosive and so reactive that in nature they are only found combined with other elements

Properties of elements in Group 8A, the noble gases  

• The noble gases, He, Ne, Ar, Kr, Xe, Ra, are nonmetals.
• The noble gases are very unreactive. They were once called the inert gases.
• The noble gases are so unreactive they are used to protect materials from reaction. Welding is done using argon atmosphere to prevent oxygen in the air from reacting with the hot welded metals.