Name an element in the fifth period (row) of the periodic table that fits each description:
a) one valence electron
b) a complete outer shell
c) five 5p electrons
The correct answer and explanation is :
Here are the correct answers for each description, followed by a detailed explanation:
a) One valence electron: Rubidium (Rb)
b) A complete outer shell: Xenon (Xe)
c) Five 5p electrons: Antimony (Sb)
Explanation (300 words):
The periodic table is arranged in periods (horizontal rows) and groups (vertical columns). The fifth period includes elements with electrons filling the fifth electron shell (n = 5). The types of orbitals involved are 5s, 4d, and 5p.
a) One valence electron — Rubidium (Rb):
Rubidium, atomic number 37, is in Group 1 (alkali metals) and Period 5. Alkali metals have one electron in their outermost shell (valence shell), which for rubidium is the 5s¹ electron. This single valence electron makes rubidium highly reactive, especially with water, and gives it characteristic metallic properties.
b) A complete outer shell — Xenon (Xe):
Xenon, atomic number 54, is a noble gas in Group 18 and Period 5. Noble gases have full outer electron shells, making them very stable and chemically inert. Xenon’s electron configuration ends in 5s² 5p⁶, completing the octet in the fifth shell. As a result, xenon rarely forms compounds under normal conditions.
c) Five 5p electrons — Antimony (Sb):
Antimony, atomic number 51, is in Group 15 and Period 5. Its electron configuration is [Kr] 4d¹⁰ 5s² 5p³. This means it has three 5p electrons, not five.
However, the element with five 5p electrons is Iodine (I), atomic number 53, with configuration [Kr] 4d¹⁰ 5s² 5p⁵.
So, the correct answer here is Iodine (I), not Antimony.
Sorry for the earlier mismatch—thank you for catching it.
Final Correct Answers:
- a) Rubidium (Rb)
- b) Xenon (Xe)
- c) Iodine (I)