how do we decide if specific element in periodic table is a metal or gas ?

The classification of elements in the periodic table as metals, nonmetals, or metalloids (semimetals) is based on their physical and chemical properties. Here are some key criteria that help determine whether a specific element is a metal, nonmetal, or metalloid!

1. Conductivity:

   • Metals: Metals are generally good conductors of electricity and heat. They have a high electrical conductivity due to the presence of mobile electrons in their structure.
   • Nonmetals: Nonmetals are typically poor conductors of electricity and heat. They do not have mobile electrons.
   • Metalloids: Metalloids have intermediate conductivity properties. They are better conductors than nonmetals but not as good as metals.

2. Physical State at Room Temperature:

   • Metals: Most metals are solid at room temperature (e.g., iron, copper).
   • Nonmetals: Nonmetals can be found in various physical states at room temperature, including gases (e.g., oxygen, nitrogen), solids (e.g., sulfur, carbon), and one liquid (bromine).
   • Metalloids: Metalloids can also have various physical states at room temperature, depending on the element (e.g., silicon is a solid, boron is a solid, arsenic is a solid).

3. Luster (Appearance):

   • Metals: Metals often have a shiny, metallic luster.
   • Nonmetals: Nonmetals usually have a dull or non-metallic appearance.
   • Metalloids: Metalloids can display a range of appearances, sometimes resembling metals and other times resembling nonmetals.

4. Malleability and Ductility:

   • Metals: Metals are typically malleable (can be hammered into thin sheets) and ductile (can be drawn into wires) due to the nature of their atomic bonding.
   • Nonmetals: Nonmetals are generally brittle and not malleable or ductile.
   • Metalloids: Metalloids may exhibit some degree of malleability and ductility but to a lesser extent than metals.

5. Chemical Behavior:

   • Metals: Metals tend to lose electrons and form positively charged ions (cations) in chemical reactions. They are more likely to act as reducing agents.
   • Nonmetals: Nonmetals tend to gain electrons and form negatively charged ions (anions) in chemical reactions. They are more likely to act as oxidizing agents.
   • Metalloids: Metalloids can exhibit a range of chemical behaviors, depending on the specific element and conditions.

6. Location in the Periodic Table:

   • Metals: The majority of elements in the periodic table, especially those on the left and toward the bottom, are metals.
   • Nonmetals: Nonmetals are primarily found on the right-hand side of the periodic table.
   • Metalloids: Metalloids are located along the "staircase" line that separates metals from nonmetals on the periodic table.