Multiple Choice
How many valence electrons does a bromine (Br) atom have?
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10. Periodic Properties of the Elements
Valence Electrons of Elements
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How many valence electrons does chromium (Cr) have in its ground state?
A
1
B
6
C
8
D
2
Verified step by step guidance1
Identify the atomic number of chromium (Cr), which is 24. This tells us the total number of electrons in a neutral chromium atom.
Write the electron configuration of chromium in its ground state. Chromium is an exception to the typical filling order, so its configuration is: $1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^1$.
Determine which electrons are considered valence electrons. For transition metals like chromium, valence electrons include those in the outermost s and d orbitals.
Count the electrons in the 4s and 3d orbitals: there is 1 electron in 4s and 5 electrons in 3d, totaling 6 valence electrons.
Conclude that chromium has 6 valence electrons in its ground state based on the electron configuration and the definition of valence electrons for transition metals.
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