Question

1. determine the number of valence electrons in each element:

a. ba
b. cs
c. ni
d. s

1. determine the number of valence electrons in each element

47
40.

Explanation:

To determine the number of valence electrons for each element, we use their positions in the periodic table (group number for main - group elements, and electron configuration analysis for transition metals):

Part a: Barium (Ba)

• Step 1: Identify the group of Ba

Barium (Ba) is an alkaline earth metal. Alkaline earth metals are in Group 2 of the periodic table.

• Step 2: Determine valence electrons based on group

For main - group elements, the number of valence electrons is equal to the group number. Since Ba is in Group 2, it has 2 valence electrons.

Part b: Cesium (Cs)

• Step 1: Identify the group of Cs

Cesium (Cs) is an alkali metal. Alkali metals are located in Group 1 of the periodic table.

• Step 2: Determine valence electrons based on group

For main - group elements, the number of valence electrons is equal to the group number. As Cs is in Group 1, it has 1 valence electron.

Part c: Nickel (Ni)

• Step 1: Write the electron configuration of Ni

The atomic number of Ni is 28. The electron configuration of Ni is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{8}4s^{2}$.

• Step 2: Identify valence electrons

For transition metals like Ni, the valence electrons include the electrons in the outermost $s$ sub - shell and the electrons in the $d$ sub - shell of the penultimate energy level. Here, the $4s$ sub - shell has 2 electrons and the $3d$ sub - shell has 8 electrons. But when considering valence electrons for chemical bonding, we mainly focus on the electrons that can participate in bonding. The $4s$ electrons and the $3d$ electrons can be involved in bonding. However, a simpler way is to know that Ni is in Group 10 (but transition metals have a different way of determining valence electrons). Another approach: The electron configuration of Ni can also be considered in terms of the outermost electrons. The $4s^{2}$ electrons and the $3d^{8}$ electrons. But for many cases, the valence electrons of Ni are considered to be 10 ( $8$ from $3d$ and $2$ from $4s$), but in some chemical contexts, it can also show variable valence. However, if we follow the general rule for transition metals, we can also calculate it from the electron configuration. The electron configuration of Ni is $[Ar]3d^{8}4s^{2}$. The valence electrons are the sum of the electrons in the $4s$ and $3d$ orbitals that are available for bonding. So, $2 + 8=10$ valence electrons. But sometimes, in some reactions, Ni can use a different number of valence electrons, but the most common way, considering its electron configuration, gives us 10 valence electrons.

Part d: Sulfur (S)

• Step 1: Identify the group of S

Sulfur (S) is a non - metal and is in Group 16 of the periodic table.

• Step 2: Determine valence electrons based on group

For main - group elements, the number of valence electrons is equal to the group number minus 10 for groups 13 - 18. For Group 16, the number of valence electrons is $16 - 10 = 6$. We can also confirm this by looking at the electron configuration of S: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{4}$. The outermost electrons are in the $3s$ and $3p$ sub - shells. The number of electrons in the outermost shell ($n = 3$) is $2+4 = 6$, so S has 6 valence electrons.

Final Answers:

a. Ba has $\boldsymbol{2}$ valence electrons.
b. Cs has $\boldsymbol{1}$ valence electron.
c. Ni has $\boldsymbol{10}$ valence electrons (in most cases, considering bonding behavior, but can have variable valence).
d. S has $\boldsymbol{6}$ valence electrons.

Answer:

To determine the number of valence electrons for each element, we use their positions in the periodic table (group number for main - group elements, and electron configuration analysis for transition metals):

Part a: Barium (Ba)

• Step 1: Identify the group of Ba

Barium (Ba) is an alkaline earth metal. Alkaline earth metals are in Group 2 of the periodic table.

• Step 2: Determine valence electrons based on group

For main - group elements, the number of valence electrons is equal to the group number. Since Ba is in Group 2, it has 2 valence electrons.

Part b: Cesium (Cs)

• Step 1: Identify the group of Cs

Cesium (Cs) is an alkali metal. Alkali metals are located in Group 1 of the periodic table.

• Step 2: Determine valence electrons based on group

For main - group elements, the number of valence electrons is equal to the group number. As Cs is in Group 1, it has 1 valence electron.

Part c: Nickel (Ni)

• Step 1: Write the electron configuration of Ni

The atomic number of Ni is 28. The electron configuration of Ni is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{8}4s^{2}$.

• Step 2: Identify valence electrons

For transition metals like Ni, the valence electrons include the electrons in the outermost $s$ sub - shell and the electrons in the $d$ sub - shell of the penultimate energy level. Here, the $4s$ sub - shell has 2 electrons and the $3d$ sub - shell has 8 electrons. But when considering valence electrons for chemical bonding, we mainly focus on the electrons that can participate in bonding. The $4s$ electrons and the $3d$ electrons can be involved in bonding. However, a simpler way is to know that Ni is in Group 10 (but transition metals have a different way of determining valence electrons). Another approach: The electron configuration of Ni can also be considered in terms of the outermost electrons. The $4s^{2}$ electrons and the $3d^{8}$ electrons. But for many cases, the valence electrons of Ni are considered to be 10 ( $8$ from $3d$ and $2$ from $4s$), but in some chemical contexts, it can also show variable valence. However, if we follow the general rule for transition metals, we can also calculate it from the electron configuration. The electron configuration of Ni is $[Ar]3d^{8}4s^{2}$. The valence electrons are the sum of the electrons in the $4s$ and $3d$ orbitals that are available for bonding. So, $2 + 8=10$ valence electrons. But sometimes, in some reactions, Ni can use a different number of valence electrons, but the most common way, considering its electron configuration, gives us 10 valence electrons.

Part d: Sulfur (S)

• Step 1: Identify the group of S

Sulfur (S) is a non - metal and is in Group 16 of the periodic table.

• Step 2: Determine valence electrons based on group

For main - group elements, the number of valence electrons is equal to the group number minus 10 for groups 13 - 18. For Group 16, the number of valence electrons is $16 - 10 = 6$. We can also confirm this by looking at the electron configuration of S: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{4}$. The outermost electrons are in the $3s$ and $3p$ sub - shells. The number of electrons in the outermost shell ($n = 3$) is $2+4 = 6$, so S has 6 valence electrons.

Final Answers:

a. Ba has $\boldsymbol{2}$ valence electrons.
b. Cs has $\boldsymbol{1}$ valence electron.
c. Ni has $\boldsymbol{10}$ valence electrons (in most cases, considering bonding behavior, but can have variable valence).
d. S has $\boldsymbol{6}$ valence electrons.