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Which of the following is considered the basic unit of matter?
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2. Atoms & Elements
The Atom
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Which element has 3 valence electrons and 4 energy levels?
A
Al
B
Ga
C
K
D
Si
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Identify the meaning of valence electrons: these are the electrons in the outermost energy level (shell) of an atom that participate in chemical bonding.
Recall that the number of valence electrons corresponds to the group number for main group elements. Elements with 3 valence electrons are typically in group 13 of the periodic table.
Determine the number of energy levels (shells) by looking at the period number of the element. The period number indicates how many energy levels the atom has.
Check each given element: Aluminum (Al) is in period 3 with 3 valence electrons, Gallium (Ga) is in period 4 with 3 valence electrons, Potassium (K) is in period 4 but has 1 valence electron, and Silicon (Si) is in period 3 with 4 valence electrons.
Conclude that the element with 3 valence electrons and 4 energy levels (period 4) is Gallium (Ga).
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