CHEM 103 EXAM 3 QUESTIONS AND
ANSWERS WITH COMPLETE
SOLUTIONS 100% CORRECT RATED
A+
Q: Why does Selenium (Se) have a lower first ionization energy than
Arsenic (As), despite being further to the right on the periodic table?
A: ✔️✔️ This occurs because Se has a fourth electron in its $4p$ subshell that
must pair up in an already occupied orbital. The resulting electron-electron
repulsion makes it easier (more energetically favorable) to remove that electron
to reach a more stable, half-filled subshell configuration. This is a classic
exception to the general periodic trend.
Q: Why is more energy released when an electron is added to Bromine (Br)
compared to Selenium (Se)?
A: ✔️✔️ Bromine is just one electron away from a noble gas electron
configuration. By gaining that single electron, it completes its octet—a highly
stable and energetically favorable state—which results in a significantly greater
release of energy (a more negative electron affinity).
Q: Why does Rubidium (Rb) react with water much more aggressively than
Sodium (Na)?
A: ✔️✔️ Both alkali metals must lose their outermost electron to react. Because
the valence electron in Rubidium is in a higher energy level (further from the
nucleus) and more shielded by inner electrons, its ionization energy is lower.
This allows the reaction to occur more readily and release energy more
violently.
Q: Fluorine (F) has an electron affinity of -332 kJ/mol. What does this value
indicate?
, A: ✔️✔️ This negative value signifies that the process is exothermic; energy is
released when a neutral Fluorine atom captures an electron. Because Fluorine is
highly electronegative and "wants" a full octet, the formation of the fluoride ion
($F^-$) is highly favorable.
one of the most negative of any elements. Briefly explain why its electron
affinity is more negative than that of oxygen. (One or two sentences). -
ANSWER ✔️✔️When an electron is added to fluorine, its octet is complete.
b) The very negative electron affinity makes fluorine extremely reactive.
Explain. -ANSWER ✔️✔️When fluorine reacts, it almost always accepts an
electron, forming fluoride ion and releasing a tremendous amount of energy (the
electron affinity). This large energy release make fluorine very reactive.
The noble gas xenon has an ionization energy of 1170 kJ/mol. The substantial
ionization energy helps to make xenon very unreactive. Explain. -ANSWER
✔️✔️Xenon cannot gain an electron (because it already has a full octet). It also
cannot readily lose an electron, because its ionization energy is so high. Thus, it
is unwilling to participate in chemical reactions.
d) Xenon's neighbor on the periodic table -ANSWER ✔️✔️iodine, also has a high
ionization energy (1020 kJ/mol). Iodine is quite reactive, however, unlike
xenon. Explain.,
Although iodine cannot readily lose an electron, it can readily gain an electron
(unlike xenon) and form a stable, complete octet. This is the usual mode of
reactivity of iodine.
Generally -ANSWER ✔️✔️radius decreases as you go across a period. Provide
the BEST explanation.,
More protons are being added to nucleus. The concentration of more protons in
the nucleus creates a
ANSWERS WITH COMPLETE
SOLUTIONS 100% CORRECT RATED
A+
Q: Why does Selenium (Se) have a lower first ionization energy than
Arsenic (As), despite being further to the right on the periodic table?
A: ✔️✔️ This occurs because Se has a fourth electron in its $4p$ subshell that
must pair up in an already occupied orbital. The resulting electron-electron
repulsion makes it easier (more energetically favorable) to remove that electron
to reach a more stable, half-filled subshell configuration. This is a classic
exception to the general periodic trend.
Q: Why is more energy released when an electron is added to Bromine (Br)
compared to Selenium (Se)?
A: ✔️✔️ Bromine is just one electron away from a noble gas electron
configuration. By gaining that single electron, it completes its octet—a highly
stable and energetically favorable state—which results in a significantly greater
release of energy (a more negative electron affinity).
Q: Why does Rubidium (Rb) react with water much more aggressively than
Sodium (Na)?
A: ✔️✔️ Both alkali metals must lose their outermost electron to react. Because
the valence electron in Rubidium is in a higher energy level (further from the
nucleus) and more shielded by inner electrons, its ionization energy is lower.
This allows the reaction to occur more readily and release energy more
violently.
Q: Fluorine (F) has an electron affinity of -332 kJ/mol. What does this value
indicate?
, A: ✔️✔️ This negative value signifies that the process is exothermic; energy is
released when a neutral Fluorine atom captures an electron. Because Fluorine is
highly electronegative and "wants" a full octet, the formation of the fluoride ion
($F^-$) is highly favorable.
one of the most negative of any elements. Briefly explain why its electron
affinity is more negative than that of oxygen. (One or two sentences). -
ANSWER ✔️✔️When an electron is added to fluorine, its octet is complete.
b) The very negative electron affinity makes fluorine extremely reactive.
Explain. -ANSWER ✔️✔️When fluorine reacts, it almost always accepts an
electron, forming fluoride ion and releasing a tremendous amount of energy (the
electron affinity). This large energy release make fluorine very reactive.
The noble gas xenon has an ionization energy of 1170 kJ/mol. The substantial
ionization energy helps to make xenon very unreactive. Explain. -ANSWER
✔️✔️Xenon cannot gain an electron (because it already has a full octet). It also
cannot readily lose an electron, because its ionization energy is so high. Thus, it
is unwilling to participate in chemical reactions.
d) Xenon's neighbor on the periodic table -ANSWER ✔️✔️iodine, also has a high
ionization energy (1020 kJ/mol). Iodine is quite reactive, however, unlike
xenon. Explain.,
Although iodine cannot readily lose an electron, it can readily gain an electron
(unlike xenon) and form a stable, complete octet. This is the usual mode of
reactivity of iodine.
Generally -ANSWER ✔️✔️radius decreases as you go across a period. Provide
the BEST explanation.,
More protons are being added to nucleus. The concentration of more protons in
the nucleus creates a
