Question detail
Which factor primarily influences the first ionisation energy of an element?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Atomic structure
Question
- A. The number of protons in the nucleus.
- B. The number of neutrons in the nucleus.
- C. The number of electrons in the outer shell.
- D. The atomic mass of the element.
Answer
The number of protons in the nucleus.
Explanation
The first ionisation energy is influenced by the nuclear charge, which is determined by the number of protons. A higher nuclear charge results in a stronger attraction between the nucleus and the electrons, leading to higher ionisation energy.
Common mistake
Confusing Ionisation Energy Definition
Students often confuse first ionisation energy with other forms of energy, such as total energy or binding energy.
First ionisation energy is defined as the energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous ions. To clarify, remember the formula: Ionisation Energy = Energy required to remove an electron from an atom. For example, for a sodium atom (Na), the first ionisation energy can be expressed as Na(g) → Na⁺(g) + e⁻. This shows that energy is needed to remove the electron, which is the essence of ionisation energy.
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