Within group 14 (group 4A) of the periodic table, which element has the highest first ionisation energy, meaning it requires the most energy to remove one electron from a gaseous atom?

Introduction / Context:
Ionisation energy is a key periodic property that describes how strongly an atom holds on to its electrons. In a given group of the periodic table, ionisation energy usually changes in a predictable way as we move from top to bottom. This question focuses on group 14, also called group 4A, which contains elements such as carbon, silicon, germanium, tin and lead. The task is to identify which of these elements has the highest first ionisation energy.

Given Data / Assumptions:
- Group 14 elements considered here include carbon, silicon, germanium, tin and lead.
- First ionisation energy refers to the energy needed to remove the outermost electron from a gaseous atom in its ground state.
- Periodic trends indicate that ionisation energy generally decreases down a group as atomic size increases.
- No unusual exceptions are assumed for this introductory level question.

Concept / Approach:
In the periodic table, ionisation energy tends to increase across a period from left to right due to increasing nuclear charge and tends to decrease down a group due to increasing atomic radius and shielding by inner electrons. In group 14, carbon is at the top, followed by silicon, germanium, tin and lead as we move downward. Because carbon is the smallest atom in the group and its valence electrons experience the strongest effective nuclear attraction, it has the highest ionisation energy among these elements. Elements further down the group have larger atomic radii and more shielding, which reduces their ionisation energies.

Step-by-Step Solution:
Step 1: List the group 14 elements in order from top to bottom: carbon, silicon, germanium, tin and lead. Step 2: Recall the general trend that ionisation energy decreases down a group because atomic radius increases and shielding by inner shells reduces the pull on valence electrons. Step 3: Recognise that carbon, being at the top of the group, has the smallest atomic size and the least shielding, so its valence electrons are held most strongly. Step 4: Understand that elements like tin and lead, near the bottom of the group, have larger atoms with more inner electrons, so their outer electrons are easier to remove. Step 5: Conclude that carbon has the highest first ionisation energy among the listed group 14 elements.

Verification / Alternative check:
If we consult tables of ionisation energies, we find that the first ionisation energy values follow the expected decreasing trend as we move from carbon down to lead. Carbon has a significantly higher first ionisation energy than silicon, germanium, tin and lead. Even without precise numerical values, the known periodic trend of decreasing ionisation energy down a group strongly supports carbon as the correct answer. This pattern is widely used in introductory chemistry to explain reactivity and bonding behaviour across a group.

Why Other Options Are Wrong:
Silicon, germanium, tin and lead are all located below carbon in group 14. Their larger atomic radii and increased electron shielding mean that their outer electrons are less tightly bound. As a result, their first ionisation energies are lower than that of carbon. Choosing any of these elements would ignore the well established trend that ionisation energy decreases down a group. Therefore, options A, B, C and E are not correct in this context.

Common Pitfalls:
Students sometimes confuse trends across a period with trends down a group, or they may recall that some elements like lead have high densities and mistakenly assume that they must also have very high ionisation energies. Another pitfall is to think that heavier elements always require more energy to ionise. Focusing on effective nuclear charge, atomic radius and shielding, and remembering that ionisation energy decreases down a group, helps avoid these errors. Recognising that carbon sits at the top of group 14 and therefore has the highest ionisation energy makes the answer straightforward.

Final Answer:
Within group 14 of the periodic table, the element with the highest first ionisation energy is Carbon.