CHEM 154 DEFINITION TERMS
core electrons - ✔✔The electrons that are not in the outermost shell of an atom
valence electrons - ✔✔Electrons on the outermost shell, which for chemical bonds
cation size - ✔✔Smaller than neutral atom due to less electrons which are pulled closer by the nucleus
anion size - ✔✔larger than neutral atom
isoelectronic - ✔✔same number of electrons, the more negative a species is, the greater its size
Effective nuclear charge (Zeff) - ✔✔the actual nuclear charge experienced by an electron, atoms further
from the nucleus experience less attraction due to shielding
Zeff Trend - ✔✔increases up and to the right
Ionization energy - ✔✔The amount of energy required to remove an electron from an
atom/molecule/ion in a gaseous state
Ionization energy trend - ✔✔increases up and to the right
Electron affinity - ✔✔the energy change that occurs when an electron is acquired by a neutral atom in a
gaseous state
Electron affinity trend - ✔✔increases up and to the right (more negative)
Electronegativity (EN) - ✔✔the relative ability of a bonded atom to attract shared electrons, calculated
value
core electrons - ✔✔The electrons that are not in the outermost shell of an atom
valence electrons - ✔✔Electrons on the outermost shell, which for chemical bonds
cation size - ✔✔Smaller than neutral atom due to less electrons which are pulled closer by the nucleus
anion size - ✔✔larger than neutral atom
isoelectronic - ✔✔same number of electrons, the more negative a species is, the greater its size
Effective nuclear charge (Zeff) - ✔✔the actual nuclear charge experienced by an electron, atoms further
from the nucleus experience less attraction due to shielding
Zeff Trend - ✔✔increases up and to the right
Ionization energy - ✔✔The amount of energy required to remove an electron from an
atom/molecule/ion in a gaseous state
Ionization energy trend - ✔✔increases up and to the right
Electron affinity - ✔✔the energy change that occurs when an electron is acquired by a neutral atom in a
gaseous state
Electron affinity trend - ✔✔increases up and to the right (more negative)
Electronegativity (EN) - ✔✔the relative ability of a bonded atom to attract shared electrons, calculated
value
