The transition elements are the metals in the central block of the periodic table, between Group 2 and Group 3. They include chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu). Their properties are similar to one another, and quite different from the Group 1 metals.
Transition metals have high melting points. Iron melts at over 1500 °C, whereas sodium melts at under 100 °C and potassium at only about 63 °C. Transition metals also have high densities, so they sink in water and feel heavy. Group 1 metals have low densities, and lithium, sodium and potassium all float on water.
Transition metals are strong and hard, which is why iron and copper are used for building and for wiring. Group 1 metals are soft and weak. You can cut them with a knife.
Transition metals are much less reactive than Group 1 metals. Sodium burns fiercely in oxygen and reacts violently with water and with halogens. Transition metals react only slowly with oxygen, water and halogens, and often need heating. Iron, for example, takes days or weeks to rust in damp air. Copper and nickel do not react with cold water at all.