Question

which of the following elements has the highest ionization energy?
ba
ne
al
cl
ca

Explanation:

Step1: Recall ionization energy trends

Ionization energy generally increases across a period (from left to right) and decreases down a group (from top to bottom) in the periodic table. Noble gases have very high ionization energy due to their stable electron configurations (full valence shells).

Step2: Analyze each element

• Ba (Barium): Group 2, period 6. Large atomic size, low ionization energy (easily loses electrons).
• Ne (Neon): Noble gas, period 2, group 18. Has a full valence shell (stable octet), so it requires a large amount of energy to remove an electron.
• Al (Aluminum): Group 13, period 3. Metalloid, ionization energy lower than noble gases.
• Cl (Chlorine): Group 17, period 3. Non - metal, but its electron configuration is not as stable as a noble gas (needs one more electron to fill valence shell), so ionization energy is lower than Ne.
• Ca (Calcium): Group 2, period 4. Metal, lower ionization energy than noble gases.

Answer:

B. Ne