Who am I ?
I am found in a thermometer. I measure your temperature.

Hint: The element which is present in our thermometers is a silvery shiny liquid. It is a d- block metal. It is even toxic and has chemical symbol Hg with atomic number 80. It belongs to the sixth period and 12th group.

Complete answer:
From our childhood, we are curious to see the shiny- silvery liquid that is present in the thermometer. Whenever the doctor checks our body temperature, we just focus on the shiny liquid. That liquid present in our thermometer is Mercury.
The mercury is a silver shiny metal which is used in the thermometer. It is the only metal which is liquid at room temperature.
It is used in thermometers because it has a high coefficient of expansion. So, with only a very small change in temperature, it shows changes that can be observed. No compound shows such characteristics.
The mercury can exist in two oxidation states (I) and (II). It usually forms stable compounds with metal-metal bonds.
Most of the mercury compounds contain mercury cations Hg (+2) and are diamagnetic.

Note:
Mercury has numerous applications. It is used in the manufacture of industrial chemicals. The mercury in gaseous form is used in fluorescent lamps. It is an ingredient in dental amalgams. A mercury compound Merbromin is a topical antiseptic that can be used to treat minor cuts and scrapes. Some transit telescopes use a basin of mercury to form flat and horizontal mirrors.