Valence Electrons of Elements: Videos & Practice Problems

In chemistry, understanding valence electrons is crucial as they are the outer shell electrons involved in forming chemical bonds. For main group elements, the number of valence electrons corresponds to the group number. For instance, chlorine, a group 7A element, has seven valence electrons. Its electron configuration is:

${\mathrm{1s}}^2{\mathrm{2s}}^2{\mathrm{2p}}^6{\mathrm{3s}}^2{\mathrm{3p}}^5$

indicating it has 10 inner core electrons and 7 valence electrons. Transition metals, labeled as group B elements, have valence electrons equal to the sum of their outermost s and d orbital electrons. For example, zinc has two s orbital electrons plus 10 d orbital electrons, totaling 12 valence electrons. Transition metals can also be identified by group numbers 3 to 12, which directly correspond to their number of valence electrons. This simplifies the process of determining valence electrons without delving into detailed electron configurations. Understanding these concepts is essential for predicting chemical reactivity and bonding behavior.

Main Group Elements Valence Electrons

Valence electrons play a crucial role in understanding the chemical behavior of elements, particularly for main group elements, which are not transition metals. The number of valence electrons corresponds directly to the group number of the element in the periodic table. Valence electrons are the outer shell electrons that participate in forming chemical bonds, while the inner core electrons are those that remain in the inner shells and do not engage in bonding.

The atomic number of an element represents the total number of electrons, which is the sum of its valence electrons and inner core electrons. For example, chlorine, which is located in group 7A, has 7 valence electrons. Its electron configuration is represented as:

1s^2 2s^2 2p^6 3s^2 3p^5

This configuration indicates that the first shell contains 2 electrons, the second shell can hold up to 8 electrons, and the third shell has 7 electrons. To visualize this, the first shell (n=1) has 2 electrons, while the second shell (n=2) is filled with 8 electrons. The outer shell (n=3) contains the 7 valence electrons, which can be represented as:

1, 2, 3, 4, 5, 6, 7

Thus, the total number of electrons in the chlorine atom is 17, which includes 7 valence electrons and 10 inner core electrons. This can be confirmed by subtracting the number of valence electrons from the total atomic number:

17 (total electrons) - 7 (valence electrons) = 10 (inner core electrons)

In summary, understanding the distribution of valence and inner core electrons is essential for predicting how elements will interact chemically, with chlorine serving as a clear example of these principles in action.

Main Group Elements Valence Electrons Example

In understanding the electron configuration of a silicon atom, it's essential to recognize that a neutral atom has an equal number of protons and electrons. Silicon, with an atomic number of 14, contains 14 electrons. The atomic number directly indicates the total number of electrons in a neutral atom.

Silicon is located in group 4A of the periodic table, which informs us that it has 4 valence electrons. Valence electrons are the electrons in the outermost shell and are crucial for determining an element's chemical properties and bonding behavior.

To find the number of inner core electrons, we subtract the number of valence electrons from the total number of electrons. In this case, we take the total of 14 electrons and subtract the 4 valence electrons:

Inner Core Electrons = Total Electrons - Valence Electrons

Inner Core Electrons = 14 - 4 = 10

Thus, a silicon atom possesses 4 valence electrons and 10 inner core electrons. This configuration is significant as it helps predict the atom's reactivity and the types of bonds it can form.

Transition Metals Valence Electrons

In the study of transition metals, understanding the number of valence electrons is crucial. For these elements, the total number of valence electrons is determined by adding the electrons in the outermost s orbital to those in the d orbital. Transition metals, also known as group B elements, span from groups 3 to 12 on the periodic table. Each transition metal has a unique configuration of s and d electrons that contributes to its valence electron count.

For example, if we analyze the outermost s and d electrons of various transition metals, we find that the first few elements have configurations such as 2 + 1, resulting in 3 valence electrons, and 2 + 2, leading to 4 valence electrons. As we progress through the series, zinc stands out with a configuration of 2 + 10, totaling 12 valence electrons. This pattern illustrates how the number of valence electrons can vary significantly among transition metals.

It's important to note that while transition metals are classified as groups 3 to 12, they also correspond to another set of group numbers. For instance, group 1A corresponds to group 1, group 2A to group 2, and so forth, up to group 8A, which is group 18. This dual classification system helps in identifying the valence electron count more efficiently.

In summary, when studying transition metals, one can either calculate the total number of s and d electrons through electron configurations or simply remember their group designations, which directly relate to their valence electron counts. This knowledge is essential for understanding the chemical behavior and properties of transition metals.

Transition Metals Valence Electrons Example

To determine the number of valence electrons in the manganese (Mn) ion with a +5 charge, it's essential to understand the electron configuration and the behavior of transition metals. Manganese is located in group 7 of the periodic table, which indicates that in its neutral state, it possesses 7 valence electrons.

When manganese forms a +5 ion, it has lost 5 electrons. This loss can be calculated directly from the number of valence electrons: 7 (neutral state) - 5 (lost electrons) = 2 valence electrons remaining.

For a more detailed approach, we can look at the electron configuration of neutral manganese, which is represented as:

${\mathrm{Ar}}^{4s}2d^5$.

When manganese loses electrons to achieve a +5 charge, the electrons are removed starting from the highest energy level. Thus, the two electrons from the 4s orbital are lost first, followed by three electrons from the 3d orbitals. After losing these five electrons, the remaining configuration would leave manganese with 2 electrons in the 3d orbitals.

In summary, the valence electrons for transition metals can be calculated as the sum of the electrons in the s and d orbitals. For manganese in the +5 oxidation state, the remaining valence electrons are 2, derived from the 3d orbitals. This understanding can be approached either through direct subtraction of lost electrons or by analyzing the electron configuration, depending on which method is more comfortable for the learner.

How many core electrons does the gallium atom possess?

• A. 2 electrons
• B. 8 electrons
• C. 18 electrons
• D. 24 electrons
• E. 28 electrons

Answer: (E)

Provide the number of valence electrons in the iron (III) ion.

• A. 2 valence electrons
• B. 5 valence electrons
• C. 8 valence electrons
• D. 3 valence electrons
• E. 6 valence electrons

Answer: (B)

Which of the following have their valence electrons in the same shell?

• A. Mg, Al, Cl
• B. B, Si, As
• C. N, As, Bi
• D. He, Ne, F

Answer: (A)

Here’s what students ask on this topic:

What are valence electrons?

Valence electrons are the electrons that reside in the outermost shell of an atom in its electron configuration. These electrons play a pivotal role in chemical reactions and bonding because they can be gained, lost, or shared with other atoms. The behavior of valence electrons determines the chemical properties of an element, including how it interacts with other elements. For example, in the formation of ionic bonds, atoms may transfer valence electrons to achieve a full outer shell, resulting in a stable electron configuration similar to that of noble gases. In covalent bonding, atoms share valence electrons to fill their outer shells. The number of valence electrons an element has can often be predicted by its group in the periodic table; for instance, all elements in Group 1 have one valence electron, while all elements in Group 17 have seven valence electrons. Understanding valence electrons is crucial for predicting the reactivity and types of compounds that an element can form.

How can valence electrons be found?

Valence electrons are the outermost electrons of an atom and play a key role in chemical bonding and reactivity. To find the number of valence electrons in an atom, you can follow these steps:

1. Identify the element on the periodic table.
2. Determine its group number (the columns on the periodic table). For main group elements (the s and p blocks), the group number often corresponds to the number of valence electrons. For example, Group 1 elements have 1 valence electron, Group 2 have 2, and so on up to Group 18, which have 8 valence electrons (except for Helium, which has 2).

For transition metals (the d block) and inner transition metals (the f block), determining valence electrons can be more complex due to their electron configurations. Typically, the valence electrons can include the outermost s and d electrons for transition metals, and the outermost s and f electrons for inner transition metals.

3. Look at the electron configuration of the element. The highest energy level (n) and the electrons within that level and the next highest d or f orbitals are considered the valence electrons.

For example, carbon has the electron configuration 1s² 2s² 2p². The electrons in the second energy level (2s² 2p²) are the valence electrons.

What are core electrons?

Core electrons are the electrons in an atom that are not part of the outermost electron shell; they are found in the inner shells. These electrons are not involved in chemical bonding and do not participate in the chemical reactions of the element. They are tightly bound to the nucleus and are shielded from the attractive forces of other atoms by the valence electrons, which are the electrons in the outermost shell that can be involved in forming chemical bonds.

The core electrons play a significant role in determining the properties of an element, such as its atomic radius, ionization energy, and electronegativity. Because they are closer to the nucleus, they experience a stronger attraction to the positive charge of the protons in the nucleus, which makes them more stable and less reactive compared to valence electrons. The number of core electrons an atom has can be determined by looking at the electron configuration of the element and counting all the electrons except those in the highest energy level (outermost shell).