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How many electrons are required to complete the outer energy level (valence shell) of a phosphorus atom?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
Multiple Choice
Which element has 2 valence electrons and is located in period 4 of the periodic table?
A
Magnesium (Mg)
B
Beryllium (Be)
C
Calcium (Ca)
D
Potassium (K)
검증된 단계별 안내1
Identify the meaning of 'valence electrons': these are the electrons in the outermost shell of an atom that participate in chemical bonding.
Recall that elements in the same group (vertical column) of the periodic table have the same number of valence electrons.
Recognize that elements with 2 valence electrons belong to Group 2, also known as the alkaline earth metals.
Determine the period (horizontal row) number, which corresponds to the highest principal energy level (n) occupied by electrons in the element.
Look for the element in Group 2 and Period 4; this element has 2 valence electrons and is located in the 4th row of the periodic table.
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