Metals And Non Metals

Step 1: Understanding the Concept:
Most metals are solid at standard room temperature (around to ).

Step 2: Detailed Explanation:
Mercury (Hg) is a unique transition metal that is distinctly liquid at normal room temperature (melting point is ).
While Gallium melts at a very low temperature ( ), it is solid at standard room temperature but can melt in your hand.
Sodium is a soft solid.
Bromine is a liquid, but it is a non-metal, not a metal.
Therefore, the only metal distinctly liquid at room temperature here is Mercury.

Step 3: Final Answer:
Mercury is the correct answer.

Step 1: Understanding the Concept:
Thermal conductivity is the ability of a material to conduct heat.
While metals are generally good conductors, some are significantly poorer than others.

Step 2: Detailed Explanation:
Silver and Copper are among the best metallic conductors of heat.
In standard high school curricula, Lead (along with Bismuth) is frequently cited as the classic example of a metal with exceptionally low thermal and electrical conductivity.

Step 3: Final Answer:
Lead is generally considered to have the lowest thermal conductivity among common metals.

Step 1: Understanding the Concept:
Alkali metals like sodium are extremely reactive elements.

Step 2: Detailed Explanation:
Sodium is placed very high in the reactivity series.
If left in the open, it reacts vigorously and spontaneously with oxygen in the air at room temperature to form sodium oxide, and it can even catch fire.
It also reacts violently with moisture (water) in the air to produce sodium hydroxide and highly combustible hydrogen gas, releasing enough heat to ignite the hydrogen.
To protect sodium and prevent accidental fires, it is kept immersed in a liquid like kerosene.
Sodium does not react with kerosene, and the liquid acts as a barrier, cutting off its contact with atmospheric oxygen and moisture.

Step 3: Final Answer:
It is kept in kerosene because it is highly reactive and would catch fire in contact with air or moisture.

Step 1: Understanding the Concept:
Metals and non-metals behave differently in chemical reactions due to their tendency to lose and gain electrons, respectively.

Step 2: Detailed Explanation:
1. Nature of Oxides: Metals react with oxygen to form basic oxides (e.g., ). Non-metals react with oxygen to form acidic or neutral oxides (e.g., ).
2. Reaction with Dilute Acids: Active metals (above hydrogen in reactivity series) react with dilute acids to displace hydrogen gas (e.g., ). Non-metals do not react with dilute acids to displace hydrogen because they are electron acceptors, not donors.

Step 3: Final Answer:
Metals form basic oxides and displace hydrogen from acids, whereas non-metals form acidic oxides and do not displace hydrogen from acids.

Step 1: Understanding the Concept:
Alloys are homogeneous mixtures of a metal with other metals or non-metals to improve properties.

Step 2: Detailed Explanation:
When one of the constituent metals in an alloy is Mercury ( ), the resulting special type of alloy is specifically called an amalgam.
For example, a mixture of mercury and silver (or tin/zinc) is known as silver amalgam, which was widely used in dentistry to fill cavities.

Step 3: Final Answer:
An amalgam is an alloy in which one of the metals is mercury.

Step 1: Understanding the Concept:
Elements react with oxygen to form oxides, which can be categorized by their acid-base properties.

Step 2: Detailed Explanation:
Generally, when non-metals react with oxygen, they form covalent oxides.
Most of these non-metallic oxides dissolve in water to form acids. For example, Sulfur dioxide ( ) forms sulfurous acid, and Carbon dioxide ( ) forms carbonic acid. Therefore, they are primarily acidic oxides.
However, some non-metal oxides do not show acidic or basic properties (e.g., Carbon monoxide , Nitrous oxide , Water ). These are called neutral oxides.

Step 3: Final Answer:
Non-metals generally form acidic oxides, though a few form neutral oxides.