Multiple Choice
An atom of element X has 17 protons. How many electrons are present in its valence shell?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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How many valence electrons does an aluminum (Al) atom have?
A
2
B
3
C
5
D
1
Verified step by step guidance1
Identify the atomic number of aluminum (Al), which is 13. This tells us the total number of electrons in a neutral Al atom.
Write the electron configuration of aluminum to understand the distribution of electrons in its shells: $1s^2 2s^2 2p^6 3s^2 3p^1$.
Recognize that valence electrons are the electrons in the outermost shell (highest principal quantum number). For aluminum, this is the third shell (n=3).
Count the electrons in the outermost shell: $3s^2$ and $3p^1$ add up to $2 + 1 = 3$ valence electrons.
Conclude that aluminum has 3 valence electrons based on the electron configuration and the definition of valence electrons.
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