5 Corrected valence electron number of Sc under "Examples"; changed from one to two
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This question may be difficult to answer because there are a couple of definitions of valence electrons. Some books and dictionaries define valence electrons as "outer shell electrons that participate in chemical bonding" and by this definition, elements can have more than 8 valence electrons as explained by F'x.

Some books and dictionaries define valence electrons as "electrons in the highest principal energy level". By this definition an element would have only 8 valence electrons because the $n-1$ $d$ orbitals fill after the $n$ $s$ orbitals, and then the $n$ $p$ orbitals fill. So, the highest principal energy level, $n$, contains the valence electrons. By this definition, the transition metals all have either 1 or 2 valence electrons (depending on how many electrons are in the $s$ vs. $d$ orbitals).

Examples:

  • Ca with two $4s$ electrons would have two valence electrons (electrons in the 4th principal energy level).
  • Sc with two $4s$ electrons and one $3d$ electron will have two valence electrons.
  • Cr with one $4s$ electron and five $3d$ electrons wouldwill have one valence electron.
  • Ga with two $4s$ electrons, ten $3d$ electrons, and one $4p$ electron would have three valence electrons.

By the other definition, they could have more since they have more "outer shell" electrons (until the $d$ shell is filled).

Using the "highest principal energy level" definition for valence electrons allows you to correctly predict the paramagnetic behavior of transition metals ions because valence electrons (the $d$ electrons) are lost first when a transition metal forms an ion.

This question may be difficult to answer because there are a couple of definitions of valence electrons. Some books and dictionaries define valence electrons as "outer shell electrons that participate in chemical bonding" and by this definition, elements can have more than 8 valence electrons as explained by F'x.

Some books and dictionaries define valence electrons as "electrons in the highest principal energy level". By this definition an element would have only 8 valence electrons because the $n-1$ $d$ orbitals fill after the $n$ $s$ orbitals, and then the $n$ $p$ orbitals fill. So, the highest principal energy level, $n$, contains the valence electrons. By this definition, the transition metals all have either 1 or 2 valence electrons (depending on how many electrons are in the $s$ vs. $d$ orbitals).

Examples:

  • Ca with two $4s$ electrons would have two valence electrons (electrons in the 4th principal energy level).
  • Sc with two $4s$ electrons and one $3d$ electron will have two valence electrons.
  • Cr with one $4s$ electron and five $3d$ electrons would have one valence electron.
  • Ga with two $4s$ electrons, ten $3d$ electrons, and one $4p$ electron would have three valence electrons.

By the other definition, they could have more since they have more "outer shell" electrons (until the $d$ shell is filled).

Using the "highest principal energy level" definition for valence electrons allows you to correctly predict the paramagnetic behavior of transition metals ions because valence electrons (the $d$ electrons) are lost first when a transition metal forms an ion.

This question may be difficult to answer because there are a couple of definitions of valence electrons. Some books and dictionaries define valence electrons as "outer shell electrons that participate in chemical bonding" and by this definition, elements can have more than 8 valence electrons as explained by F'x.

Some books and dictionaries define valence electrons as "electrons in the highest principal energy level". By this definition an element would have only 8 valence electrons because the $n-1$ $d$ orbitals fill after the $n$ $s$ orbitals, and then the $n$ $p$ orbitals fill. So, the highest principal energy level, $n$, contains the valence electrons. By this definition, the transition metals all have either 1 or 2 valence electrons (depending on how many electrons are in the $s$ vs. $d$ orbitals).

Examples:

  • Ca with two $4s$ electrons would have two valence electrons (electrons in the 4th principal energy level).
  • Sc with two $4s$ electrons and one $3d$ electron will have two valence electrons.
  • Cr with one $4s$ electron and five $3d$ electrons will have one valence electron.
  • Ga with two $4s$ electrons, ten $3d$ electrons, and one $4p$ electron would have three valence electrons.

By the other definition, they could have more since they have more "outer shell" electrons (until the $d$ shell is filled).

Using the "highest principal energy level" definition for valence electrons allows you to correctly predict the paramagnetic behavior of transition metals ions because valence electrons (the $d$ electrons) are lost first when a transition metal forms an ion.

4 Corrected valence electron number of Sc under "Examples"; changed from one to two; had to change "would" to "will" to meet editing character number requirements
source | link

This question may be difficult to answer because there are a couple of definitions of valence electrons. Some books and dictionaries define valence electrons as "outer shell electrons that participate in chemical bonding" and by this definition, elements can have more than 8 valence electrons as explained by F'x.

Some books and dictionaries define valence electrons as "electrons in the highest principal energy level". By this definition an element would have only 8 valence electrons because the $n-1$ $d$ orbitals fill after the $n$ $s$ orbitals, and then the $n$ $p$ orbitals fill. So, the highest principal energy level, $n$, contains the valence electrons. By this definition, the transition metals all have either 1 or 2 valence electrons (depending on how many electrons are in the $s$ vs. $d$ orbitals).

Examples:

  • Ca with two $4s$ electrons would have two valence electrons (electrons in the 4th principal energy level).
  • Sc with two $4s$ electrons and one $3d$ electron wouldwill have onetwo valence electronelectrons.
  • Cr with one $4s$ electron and five $3d$ electrons would have one valence electron.
  • Ga with two $4s$ electrons, ten $3d$ electrons, and one $4p$ electron would have three valence electrons.

By the other definition, they could have more since they have more "outer shell" electrons (until the $d$ shell is filled).

Using the "highest principal energy level" definition for valence electrons allows you to correctly predict the paramagnetic behavior of transition metals ions because valence electrons (the $d$ electrons) are lost first when a transition metal forms an ion.

This question may be difficult to answer because there are a couple of definitions of valence electrons. Some books and dictionaries define valence electrons as "outer shell electrons that participate in chemical bonding" and by this definition, elements can have more than 8 valence electrons as explained by F'x.

Some books and dictionaries define valence electrons as "electrons in the highest principal energy level". By this definition an element would have only 8 valence electrons because the $n-1$ $d$ orbitals fill after the $n$ $s$ orbitals, and then the $n$ $p$ orbitals fill. So, the highest principal energy level, $n$, contains the valence electrons. By this definition, the transition metals all have either 1 or 2 valence electrons (depending on how many electrons are in the $s$ vs. $d$ orbitals).

Examples:

  • Ca with two $4s$ electrons would have two valence electrons (electrons in the 4th principal energy level).
  • Sc with two $4s$ electrons and one $3d$ electron would have one valence electron.
  • Cr with one $4s$ electron and five $3d$ electrons would have one valence electron.
  • Ga with two $4s$ electrons, ten $3d$ electrons, and one $4p$ electron would have three valence electrons.

By the other definition, they could have more since they have more "outer shell" electrons (until the $d$ shell is filled).

Using the "highest principal energy level" definition for valence electrons allows you to correctly predict the paramagnetic behavior of transition metals ions because valence electrons (the $d$ electrons) are lost first when a transition metal forms an ion.

This question may be difficult to answer because there are a couple of definitions of valence electrons. Some books and dictionaries define valence electrons as "outer shell electrons that participate in chemical bonding" and by this definition, elements can have more than 8 valence electrons as explained by F'x.

Some books and dictionaries define valence electrons as "electrons in the highest principal energy level". By this definition an element would have only 8 valence electrons because the $n-1$ $d$ orbitals fill after the $n$ $s$ orbitals, and then the $n$ $p$ orbitals fill. So, the highest principal energy level, $n$, contains the valence electrons. By this definition, the transition metals all have either 1 or 2 valence electrons (depending on how many electrons are in the $s$ vs. $d$ orbitals).

Examples:

  • Ca with two $4s$ electrons would have two valence electrons (electrons in the 4th principal energy level).
  • Sc with two $4s$ electrons and one $3d$ electron will have two valence electrons.
  • Cr with one $4s$ electron and five $3d$ electrons would have one valence electron.
  • Ga with two $4s$ electrons, ten $3d$ electrons, and one $4p$ electron would have three valence electrons.

By the other definition, they could have more since they have more "outer shell" electrons (until the $d$ shell is filled).

Using the "highest principal energy level" definition for valence electrons allows you to correctly predict the paramagnetic behavior of transition metals ions because valence electrons (the $d$ electrons) are lost first when a transition metal forms an ion.

3 fixed very important typo; made formatting consistent
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This question may be difficult to answer because there are a couple of definitions of valence electrons. Some books and dictionaries define valence electrons as "outer shell electrons that participate in chemical boning"bonding" and by this definition, elements can have more than 8 valence electrons as explained by F'x.

Some books and dictionaries define valence electrons as "electrons in the highest principal energy level". By this definition an element would have only 8 valence electrons because the n-1$n-1$ d$d$ orbitals fill after the n$n$ s$s$ orbitals, and then the n$n$ p$p$ orbitals fill. So, the highest principal energy level, n$n$, contains the valence electrons. By this definition, the transition metals all have either 1 or 2 valence electrons (depending on how many electrons are in the s$s$ vs. d$d$ orbitals).

Example Examples:

  • Ca with two 4s$4s$ electrons would have 2two valence electrons (electrons in the 4th principal energy level).
  • Sc with two 4s$4s$ electrons and one 3d$3d$ electron would have 2one valence electrons (electrons in the 4th principal energy level)electron.
  • Cr with one 4s$4s$ electron and 5 3dfive $3d$ electrons would have 1one valence electron.
  • Ga with two 4s$4s$ electrons, ten 3d$3d$ electrons, and 1 4pone $4p$ electron would have 3three valence electrons.

By the other definition, they could have more since they have more "outer shell" electrons (until the d$d$ shell is filled).

Using the "highest principal energy level" definition for valence electrons allows you to correctly predict the paramagnetic behavior of transition metals ions because valence electrons (the s$d$ electrons) are lost first when a transition metal forms an ion.

This question may be difficult to answer because there are a couple of definitions of valence electrons. Some books and dictionaries define valence electrons as "outer shell electrons that participate in chemical boning" and by this definition, elements can have more than 8 valence electrons as explained by F'x.

Some books and dictionaries define valence electrons as "electrons in the highest principal energy level". By this definition an element would have only 8 valence electrons because the n-1 d orbitals fill after the n s orbitals, and then the n p orbitals fill. So, the highest principal energy level, n, contains the valence electrons. By this definition, the transition metals all have either 1 or 2 valence electrons (depending on how many electrons are in the s vs. d orbitals).

Example

  • Ca with two 4s electrons would have 2 valence electrons
  • Sc with two 4s electrons and one 3d electron would have 2 valence electrons (electrons in the 4th principal energy level)
  • Cr with one 4s electron and 5 3d electrons would have 1 valence electron
  • Ga with two 4s electrons, ten 3d electrons, and 1 4p electron would have 3 valence electrons.

By the other definition, they could have more since they have more "outer shell" electrons (until the d shell is filled).

Using the "highest principal energy level" definition for valence electrons allows you to correctly predict the paramagnetic behavior of transition metals ions because valence electrons (the s electrons) are lost first when a transition metal forms an ion.

This question may be difficult to answer because there are a couple of definitions of valence electrons. Some books and dictionaries define valence electrons as "outer shell electrons that participate in chemical bonding" and by this definition, elements can have more than 8 valence electrons as explained by F'x.

Some books and dictionaries define valence electrons as "electrons in the highest principal energy level". By this definition an element would have only 8 valence electrons because the $n-1$ $d$ orbitals fill after the $n$ $s$ orbitals, and then the $n$ $p$ orbitals fill. So, the highest principal energy level, $n$, contains the valence electrons. By this definition, the transition metals all have either 1 or 2 valence electrons (depending on how many electrons are in the $s$ vs. $d$ orbitals).

Examples:

  • Ca with two $4s$ electrons would have two valence electrons (electrons in the 4th principal energy level).
  • Sc with two $4s$ electrons and one $3d$ electron would have one valence electron.
  • Cr with one $4s$ electron and five $3d$ electrons would have one valence electron.
  • Ga with two $4s$ electrons, ten $3d$ electrons, and one $4p$ electron would have three valence electrons.

By the other definition, they could have more since they have more "outer shell" electrons (until the $d$ shell is filled).

Using the "highest principal energy level" definition for valence electrons allows you to correctly predict the paramagnetic behavior of transition metals ions because valence electrons (the $d$ electrons) are lost first when a transition metal forms an ion.

2 Added the last sentence
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