Among the elements oxygen, gold, silver and manganese, which one has the lowest melting point?

Introduction / Context:
This question asks you to compare melting points of different elements from both metals and non metals. Melting point is the temperature at which a solid turns into a liquid. Generally, metals with strong metallic bonding have high melting points, whereas molecular substances composed of small molecules often have very low melting points. Recognising that oxygen is a diatomic gas at room temperature while the others are solid metals helps you choose the correct answer.

Given Data / Assumptions:

• Elements to compare: oxygen, gold, silver and manganese.
• We must identify the one with the lowest melting point.
• We assume standard atmospheric pressure and pure elements.

Concept / Approach:
Oxygen at normal conditions exists as O2 molecules and is a gas at room temperature. Its melting point is very low, far below zero degrees Celsius. In contrast, gold, silver and manganese are metallic solids with relatively high melting points due to strong metallic bonding. Therefore, the gaseous element oxygen will have the lowest melting point among the four.

Step-by-Step Solution:
Step 1: Classify the elements. Oxygen is a non metal that exists as diatomic O2 gas at room temperature. Gold, silver and manganese are solid metals. Step 2: Recall that gases at room temperature must have very low melting and boiling points, because their intermolecular forces are weak. Step 3: Oxygen becomes a pale blue liquid at very low temperatures and then a solid at even lower temperatures, so its melting point is far below the melting points of typical metals. Step 4: Gold and silver are noble metals with strong metallic bonds and have high melting points in the range of hundreds of degrees Celsius. Step 5: Manganese is also a metal and has a high melting point, again much higher than that of molecular oxygen. Step 6: Since oxygen is already a gas at ordinary conditions, its melting point is the lowest among the given elements. Step 7: Therefore, the correct answer is oxygen.

Verification / Alternative check:
Approximate data from reference tables show that oxygen melts at about minus two hundred degrees Celsius, while the melting points of gold, silver and manganese are all above several hundred or more than one thousand degrees Celsius. Although you are not expected to know the exact numbers in a typical exam, recognising that metals usually melt at high temperatures and gases at very low temperatures is sufficient to compare which is lowest.

Why Other Options Are Wrong:
Gold, silver and manganese are solid metals at room temperature and require high temperatures to melt. Their metallic bonds involve a lattice of positive metal ions embedded in a sea of delocalised electrons, which requires significant energy to break. Therefore, their melting points are far higher than that of oxygen. The option stating that all have similar melting points is clearly incorrect because one is a gas and the others are solids under normal conditions.

Common Pitfalls:
A potential mistake is to recall that gold and silver are relatively soft metals and assume that softness means low melting point. In reality, softness refers to mechanical hardness, not melting point. Gold still has a high melting point despite being malleable. Another pitfall is to forget that oxygen is a gas at room temperature and treat it like a solid element. Remembering the physical state of elements at room temperature can help you compare their melting and boiling points more reliably.

Final Answer:
Among oxygen, gold, silver and manganese, the element with the lowest melting point is oxygen.