WKS - Chem 1 Name: Answer Key
Ionization Energy & Electronegativity Period: Date:
Ionization Energy
1. What is ionization energy?
It is the energy needed to remove an electron from an atom in the gas phase. The process is denoted by:
Ionization Energy + X → X+ + e–
2. If the ionization energy is high, then it is relatively (easy, hard) to remove an electron from the atom.
3. As the atomic radius increases (down a column/family), the ionization energy gets (lower, higher).
Explain this trend in terms of distance between the valence electrons and the nucleus, and amount of
shielding by core electrons.
Moving down a column, the outer electrons are in higher energy levels that are farther from the nucleus
and more shielded by core electrons, so the attraction of the electrons to the nucleus decreases, making it
easier to remove an electron.
4. Moving left to right in a period/row, the ionization energy gets (lower, higher). Explain this trend in
terms of effective nuclear charge (Zeff) and atomic radius.
Moving right in a period, Zeff increases, pulling the electrons closer to the nucleus, making them more
attracted to the nucleus and harder to remove.
5. In general, do metals or non-metals have higher ionization energy? Why?
Non-metals have higher IE because they have higher Zeff and are smaller, so their electrons are more
strongly attracted to the nucleus.
6. Which element has higher ionization energy: C or O? Why?
O has higher IE. It is farther to the right, so it is smaller with higher Zeff and has a higher attraction
between the nucleus and electrons.
7. Which element has higher ionization energy: Na or Rb? Why?
Na has higher IE. It is higher in its family, so it is smaller with its outer electrons closer to the nucleus
and more attracted.
Electronegativity
8. What is electronegativity?
Electronegativity is the relative tendency of an atom to attract electrons from another atom in a bond.
9. If the electronegativity is high, then it is attracts electrons (weakly, strongly).
