CHEM 1211 exam 4 Questions and Answers Solved Correctly Latest Update 2025-2026
covalent radius - Answers half the distance between two nonmetal nuclei
metallic radius - Answers half of the total distance between the nuclei of two adjacent atoms in a
crystalline solid metal
what are the trends of atomic radii? - Answers decreases across a period (horizontal row) and increases
down a group (column)
why does atomic radius decrease across a period (horizontal row)? - Answers Number of protons in the
nucleus and effective nuclear charge increase, so the nucleus more strongly attracts orbital electrons
and pulls them closer to it, while electron shielding remains similar.
why does effective nuclear charge increase across a period? - Answers the number of protons increase
and this causes effective nuclear charge to increase
what kind of electrons help in shielding? - Answers core electrons
do valence electrons help in shielding? - Answers no
what is effective nuclear charge (Zeff)? - Answers the actual attractice (positive charge) that electrons
feel from the nucleus
why does Zeff increase across the periodic table? - Answers shielding
how can we calculate effective nuclear charge? - Answers atomic number - number of core electrons
why does atomic radius increase down a group? - Answers number of energy levels (n) increase, greater
distance between nucleus and outermost orbital
order of atomic sizes of ions - Answers anion > neutral > cation
anion - Answers negatively charged ion
cation - Answers positively charged ion
why are anions bigger than neutral atoms? - Answers there is weaker nuclear attraction and larger
radius.
isoelectronic ions - Answers ions containing the same number of electrons
if atoms are isoelectronic, the atom with the _____ charge will be the smallest. - Answers highest, most
positive
ionization energy - Answers the amount of energy required to move an electron from a neutral atom or
ion in the gaseous phase
, ionization is always (endothermic/exothermic) - Answers endothermic
endothermic - Answers absorbs heat and energy
first ionization energy - Answers energy required to remove the first electron
second ionization energy - Answers energy required to remove the second electron
as nuclear attractions increase, it becomes ______ to remove electrons - Answers harder
second & higher ionization energies are always ______ than first ionization energies - Answers higher
removing a valence electron is ______ than removing a core electron - Answers easier
trends of first ionization energy - Answers increases across a period
why does first ionization energy increase across a period? - Answers effective nuclear charge increases
what groups have exceptions in ionization energy trends? - Answers groups 2 & 13, groups 15 & 16
what is the ionization energy anomaly in group 2? - Answers energy is a little higher than expected
what is the ionization energy anomaly in group 13? - Answers energy is a bit lower than expected
why does Be have a higher IE than B? - Answers Be has full 1s and 2s levels making it harder to remove
an electron
what is the ionization energy anomaly in group 15? - Answers nitrogen has half-filled orbitals in 2p group
and it is harder than expected to remove electrons
what is the ionization energy anomaly in group 16? - Answers oxygen; the electron repulsion helps to
remove electrons easier than in nitrogen. requires less energy than expected
how to determine which given element has highest second ionization energy - Answers write electron
configuration and take away 2 electrons, if one of them is a core electron than it has high second
ionization energy
electron affinity - Answers amount of energy released when a neutral atom gains an electron to a
gaseous phase
electron affinity is (endothermic/exothermic) - Answers exothermic
exothermic - Answers energy is released
is electron affinity positive or negative? - Answers negative
electron affinity trends - Answers increases across a row, decreases down a group
example of electron affinity with X - Answers X(g) + e- → X-(g)
covalent radius - Answers half the distance between two nonmetal nuclei
metallic radius - Answers half of the total distance between the nuclei of two adjacent atoms in a
crystalline solid metal
what are the trends of atomic radii? - Answers decreases across a period (horizontal row) and increases
down a group (column)
why does atomic radius decrease across a period (horizontal row)? - Answers Number of protons in the
nucleus and effective nuclear charge increase, so the nucleus more strongly attracts orbital electrons
and pulls them closer to it, while electron shielding remains similar.
why does effective nuclear charge increase across a period? - Answers the number of protons increase
and this causes effective nuclear charge to increase
what kind of electrons help in shielding? - Answers core electrons
do valence electrons help in shielding? - Answers no
what is effective nuclear charge (Zeff)? - Answers the actual attractice (positive charge) that electrons
feel from the nucleus
why does Zeff increase across the periodic table? - Answers shielding
how can we calculate effective nuclear charge? - Answers atomic number - number of core electrons
why does atomic radius increase down a group? - Answers number of energy levels (n) increase, greater
distance between nucleus and outermost orbital
order of atomic sizes of ions - Answers anion > neutral > cation
anion - Answers negatively charged ion
cation - Answers positively charged ion
why are anions bigger than neutral atoms? - Answers there is weaker nuclear attraction and larger
radius.
isoelectronic ions - Answers ions containing the same number of electrons
if atoms are isoelectronic, the atom with the _____ charge will be the smallest. - Answers highest, most
positive
ionization energy - Answers the amount of energy required to move an electron from a neutral atom or
ion in the gaseous phase
, ionization is always (endothermic/exothermic) - Answers endothermic
endothermic - Answers absorbs heat and energy
first ionization energy - Answers energy required to remove the first electron
second ionization energy - Answers energy required to remove the second electron
as nuclear attractions increase, it becomes ______ to remove electrons - Answers harder
second & higher ionization energies are always ______ than first ionization energies - Answers higher
removing a valence electron is ______ than removing a core electron - Answers easier
trends of first ionization energy - Answers increases across a period
why does first ionization energy increase across a period? - Answers effective nuclear charge increases
what groups have exceptions in ionization energy trends? - Answers groups 2 & 13, groups 15 & 16
what is the ionization energy anomaly in group 2? - Answers energy is a little higher than expected
what is the ionization energy anomaly in group 13? - Answers energy is a bit lower than expected
why does Be have a higher IE than B? - Answers Be has full 1s and 2s levels making it harder to remove
an electron
what is the ionization energy anomaly in group 15? - Answers nitrogen has half-filled orbitals in 2p group
and it is harder than expected to remove electrons
what is the ionization energy anomaly in group 16? - Answers oxygen; the electron repulsion helps to
remove electrons easier than in nitrogen. requires less energy than expected
how to determine which given element has highest second ionization energy - Answers write electron
configuration and take away 2 electrons, if one of them is a core electron than it has high second
ionization energy
electron affinity - Answers amount of energy released when a neutral atom gains an electron to a
gaseous phase
electron affinity is (endothermic/exothermic) - Answers exothermic
exothermic - Answers energy is released
is electron affinity positive or negative? - Answers negative
electron affinity trends - Answers increases across a row, decreases down a group
example of electron affinity with X - Answers X(g) + e- → X-(g)
