Among the following elements, which one has the lowest melting point under standard atmospheric conditions?

Introduction / Context:
Melting point is a fundamental physical property that tells us the temperature at which a substance changes from solid to liquid under a given pressure. Comparing melting points helps us understand bonding, structure and phase at room temperature. Among common elements, some are solid, some are liquid and some are gases at ordinary conditions. This question asks which element from the given list has the lowest melting point, meaning it requires the least heating to turn from solid to liquid or may even already be liquid near room temperature.

Given Data / Assumptions:

• The elements listed are bromine, zinc, lead, calcium and aluminium.
• Zinc, lead, calcium and aluminium are metals that are normally solids at room temperature.
• Bromine is a halogen and is one of the very few elements that exist as a liquid at or near room temperature.
• We consider approximate melting points under standard atmospheric pressure.

Concept / Approach:
Metals typically have relatively high melting points because of strong metallic bonding, although there are exceptions such as mercury. Bromine is a non metallic element that exists as a diatomic molecular liquid (Br2) at room temperature, indicating that its melting point is just below room temperature. This means bromine has a much lower melting point than the listed metals. Therefore, the approach is to recall that bromine is liquid at room temperature and conclude that its melting point is the lowest among the options provided.

Step-by-Step Solution:
Step 1: Note that zinc, lead, calcium and aluminium are all metallic solids at ordinary room temperature. Step 2: Metals generally have higher melting points due to the strong attraction between metal ions and the sea of electrons in metallic bonding. Step 3: Bromine is unusual because it is a dark red brown liquid at room temperature, indicating that its melting point is below room temperature. Step 4: For bromine to be liquid at room temperature, its melting point must be at a much lower temperature than that of typical metals such as zinc or aluminium. Step 5: Lead and zinc have comparatively lower melting points among metals but still significantly higher than bromine, which transitions from solid to liquid at a temperature just below room temperature. Step 6: Therefore, bromine clearly has the lowest melting point among the given elements.

Verification / Alternative check:
Reference data show that bromine has a melting point around minus seven degrees Celsius, so it is liquid at normal room temperatures. In contrast, zinc melts at a few hundred degrees Celsius, lead melts above 300 degrees Celsius, calcium melts above 800 degrees Celsius and aluminium melts above 600 degrees Celsius. These values confirm that bromine has a melting point far below those of the listed metals. The fact that bromine is liquid in laboratory bottles at room temperature provides an everyday verification of its very low melting point compared with typical metals.

Why Other Options Are Wrong:
Option B, zinc, does have a relatively moderate melting point but it is still much higher than that of bromine and zinc is solid at room temperature. Option C, lead, melts at a lower temperature than many structural metals, but again it is solid at room temperature and requires significant heating to melt. Option D, calcium, is a reactive metal with a relatively high melting point. Option E, aluminium, is also a structural metal with a high melting point. None of these metals come close to bromine in having such a low melting point that the element is liquid near room temperature.

Common Pitfalls:
Students sometimes overlook the fact that bromine is not a metal and instead focus only on the list of metals, comparing their melting points. Another common error is confusing bromine with mercury, which is the well known liquid metal at room temperature. While mercury has a very low melting point among metals, it is not listed as an option here. To avoid confusion, remember that among the halogens, bromine is liquid at room temperature, making its melting point lower than that of most ordinary metals, including all of the metals listed in this question.

Final Answer:
The element among the options that has the lowest melting point is Bromine.