CEM EXAM 2 QUESTIONS AND
ANSWERS WITH SOLUTIONS 2024
What are core electrons? - ANSWER Low in energy and close to the nucleus- within the closed shell
-A closed shell of electrons are very stable and don't participate in reactions
What are valence electrons? - ANSWER Higher in energy and outside of a closed shell
-These are the electrons that determine reactivity
Atomic radius - ANSWER Half the distance between the two nuclei
Does atomic radius increase or decrease down a group? - ANSWER Increase
Does atomic radius increase or decrease across a row? - ANSWER Decrease
What does the size of an atom depend on? - ANSWER 1. Attractions of the protons and electrons
2. Repulsions between the electrons in the atom
What state does the atomic radius represent? - ANSWER Where the forces of attraction between the
electrons and the protons are equal to the forces of repulsion between the electrons
Why does atomic radius decrease across a row? - ANSWER Effective nuclear charge. Atoms with a high
effective nuclear charge "hold onto their electrons" tightly. Maling the electrons more strongly attached
to the nucleus. Which is why atomic radius decreases across a row.
Effective nuclear charge - ANSWER Core electrons "cancel out" the positive charge from the same
number of protons
Each electron in the valence shell feels the effect of the protons that are left out. Atoms with a high
effective nuclear charge "hold onto their electrons" tightly. Maling the electrons more strongly attached
to the nucleus. Which is why atomic radius decreases across a row.
, Effective nuclear charge formula - ANSWER Z(enc)=z(actual nuclear charge[# protons])-S(# core
electrons)
T/F Effective nuclear charge increases across a row - ANSWER True
Ion - ANSWER Atoms in which electrons have been added or removed
If an electron is removed from an atom, what is the charge of the ion? - ANSWER Positive (the outermost
electron is removed resulting in a cation)
What is a cation? - ANSWER positively charged atom or molecule
What has a larger radius the atom or the cation of the atom? - ANSWER The regular atom because more
electrons means a greater electron electron repulsion
If an electron is added to an atom, what is the charge of the ion? - ANSWER Negative(an electron is
added to the next available (lowest energy) orbital
What is an anion? - ANSWER Negatively charged atom or molecule, it gained an electron
What has a larger radius the atom or the anion of the atom? - ANSWER The anion because you add an
electron which makes a greater electron electron repulsion
Ionization Energy - ANSWER nergy required to remove an electron from an atom in the gas phase
T/F Ionization energy decreases down a group/ column - ANSWER True
T/F Ionization energy increases across a row - ANSWER True
What are Ionization energies affected by? - ANSWER -Size of atom/ion(smaller size= higher IE)
ANSWERS WITH SOLUTIONS 2024
What are core electrons? - ANSWER Low in energy and close to the nucleus- within the closed shell
-A closed shell of electrons are very stable and don't participate in reactions
What are valence electrons? - ANSWER Higher in energy and outside of a closed shell
-These are the electrons that determine reactivity
Atomic radius - ANSWER Half the distance between the two nuclei
Does atomic radius increase or decrease down a group? - ANSWER Increase
Does atomic radius increase or decrease across a row? - ANSWER Decrease
What does the size of an atom depend on? - ANSWER 1. Attractions of the protons and electrons
2. Repulsions between the electrons in the atom
What state does the atomic radius represent? - ANSWER Where the forces of attraction between the
electrons and the protons are equal to the forces of repulsion between the electrons
Why does atomic radius decrease across a row? - ANSWER Effective nuclear charge. Atoms with a high
effective nuclear charge "hold onto their electrons" tightly. Maling the electrons more strongly attached
to the nucleus. Which is why atomic radius decreases across a row.
Effective nuclear charge - ANSWER Core electrons "cancel out" the positive charge from the same
number of protons
Each electron in the valence shell feels the effect of the protons that are left out. Atoms with a high
effective nuclear charge "hold onto their electrons" tightly. Maling the electrons more strongly attached
to the nucleus. Which is why atomic radius decreases across a row.
, Effective nuclear charge formula - ANSWER Z(enc)=z(actual nuclear charge[# protons])-S(# core
electrons)
T/F Effective nuclear charge increases across a row - ANSWER True
Ion - ANSWER Atoms in which electrons have been added or removed
If an electron is removed from an atom, what is the charge of the ion? - ANSWER Positive (the outermost
electron is removed resulting in a cation)
What is a cation? - ANSWER positively charged atom or molecule
What has a larger radius the atom or the cation of the atom? - ANSWER The regular atom because more
electrons means a greater electron electron repulsion
If an electron is added to an atom, what is the charge of the ion? - ANSWER Negative(an electron is
added to the next available (lowest energy) orbital
What is an anion? - ANSWER Negatively charged atom or molecule, it gained an electron
What has a larger radius the atom or the anion of the atom? - ANSWER The anion because you add an
electron which makes a greater electron electron repulsion
Ionization Energy - ANSWER nergy required to remove an electron from an atom in the gas phase
T/F Ionization energy decreases down a group/ column - ANSWER True
T/F Ionization energy increases across a row - ANSWER True
What are Ionization energies affected by? - ANSWER -Size of atom/ion(smaller size= higher IE)
