Answer:

In the periodic table above, black squares indicate elements which are solids at room temperature (about 22ºC)*, those in blue squares are liquids at room temperature, and those in red squares are gases at room temperature.

Most of the metals are solids under "ordinary" conditions (i.e., 25ºC, 1 atmosphere of pressure, etc.), with the exception of mercury (Hg, element 80), which solidifies at -39ºC, and is a freely-flowing liquid at room temperature. Gallium (Ga, element 31) melts at 30ºC, slightly above room temperature, but is often indicated as a liquid on periodic tables, since the solid metal literally melts when held in the hand (since body temperature is about 37ºC). (Since cesium melts at 28ºC, and francium at 27ºC, they are also indicated in blue on some tables, but anyone who holds cesium in their hands won't be holding much of anything afterwards! See the page on alkali metals for more on cesium's high reactivity.)

Several of the nonmetals are gases in their elemental form. Elemental hydrogen (H, element 1), nitrogen (N, element 7), oxygen (O, element 8), fluorine (F, element 9), and chlorine (Cl, element 17) are all gases at room temperature, and are found as diatomic molecules (H2, N2, O2, F2, Cl2). Bromine (Br, element 35), also found as a diatomic molecule (Br2), is a liquid at room temperature, solidifying at -7.2ºC. The noble gases of Group 8A (He, Ne, Ar, Kr, Xe, and Rn) are all gases at room temperature (as the name of the group implies); since they are all unreactive, monatomic elements, their boiling points are extremely low.

Below is a table of the melting points, boiling points, and densities of the