Multiple Choice
How many valence electrons are present in the nitrate ion, NO_3^-?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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Which of the following is a requirement for an atom to have an expanded valence shell (expanded octet)?
A
The atom must be in period 3 or higher of the periodic table.
B
The atom must be in period 2 of the periodic table.
C
The atom must be a noble gas.
D
The atom must have exactly eight valence electrons.
Verified step by step guidance1
Understand the concept of an expanded valence shell: This occurs when an atom has more than eight electrons in its valence shell, exceeding the octet rule.
Recall that the octet rule generally applies to atoms in period 2 of the periodic table, which can hold a maximum of 8 electrons in their valence shell (2s and 2p orbitals).
Recognize that atoms in period 3 or higher have access to d orbitals in addition to s and p orbitals, allowing them to accommodate more than 8 electrons in their valence shell.
Therefore, for an atom to have an expanded valence shell, it must be in period 3 or beyond, where d orbitals are available for bonding.
Conclude that the requirement for an expanded octet is that the atom must be in period 3 or higher of the periodic table.
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