Valence Electrons of Elements - Online Tutor, Practice Problems & Exam Prep

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.

Valence Electrons of Elements

Now when it comes to valence electrons, we're going to say that for main group elements, so basically not the transition metals, we're going to say the number of valence electrons equals the group number of the element. And when we say valence electrons, the valence electrons are just your outer shell electrons involved in forming chemical bonds. The intercore electrons are just all the remaining electrons that are not valence electrons.

And we're going to say here that your atomic number can be thought of as your total number of electrons, and that equals just all your valence electrons plus your inner core electrons. If we take a look here, we have chlorine. Chlorine is in Group 7A, so it has seven valence electrons. Its electron configuration is 1S22S22P63S23P5. Here. Remember the number in front tells us the shell number. So here this would be shell I, shell two and shell 3.

If we have a representation of the atom, like we do here, the first shell has two electrons in it. The second shell, n = 2, has a total of 8 electrons in it. So if you count 12345678 all the way around and then we can say here that the outer shell has seven electrons total in it. So let's add the additional 2 electrons that we need. So we have 123456 and then seven. Those are our seven total electrons.

So here we have the visual representation of the atom. We're using the electron configuration to justify this representation of the chlorine atom. But for simplicity just say group number of the element. Main group element is 7 A, so it has seven valence electrons. If you subtract that, then what's left will be your inner core electrons, which would just be 10 and we would see yes, in fact it is 10 because when you add up these numbers it gives you 10. And when you look at the visual representation of the chlorine atom, you'd also see that there are 10 inner core electrons.

Valence Electrons of Elements Example 1

Here it says how many inner core and valence electrons would a silicon atom possess. So atom means that it's a neutral element. And when we look, silicon has an atomic number of 14 on the periodic table. So remember your atomic number which is connected to your total number of electrons equals your valence electrons, which for main group element is just your group number plus your inner core electrons.

Here the atomic number again we said is 14. Silicon is in Group 4A on the periodic table. Since it's in Group 4A, it has four valence electrons, so we already know we have 4 valence electrons, and all we have to do here to find the number of intercore electrons is subtract 4 from both sides and what's left is 10.

That 10 would equal the number of intercore electrons. So we'd say that's the silicon atom has four valence electrons in Group 4A, and it has 10 inner core electrons.

Valence Electrons of Elements

Now with transition metals, we're going to say the number of valence electrons equals their outermost S orbital electrons plus their D orbital electrons. And here, remember, your transition metal elements are known as your Group B elements. So we know there's 3B all the way to 1B all the way to 8B. But you don't look at that to determine the number of valence electrons.

Let's take a look. Here I've listed the outermost S orbitals and the D orbital electrons for each of the transition metals. If we look at them, this is 2+1=3, 2+2=4, and it goes on and on. Then when we get to zinc, we see that it is 2+10=12. Remember, besides classifying transition metals as Group B elements, if you look at a full out, umm periodic table that we did in earlier chapters, you'll see that these groups also have another set of numbers for their group identity.

This would be group three, group 456-789-1011 and 12. Remember our main group elements, groups 1A to 8A, but they also have another set of numbers that describe them. Group 1A is Group One, Group 2A is group two. Group 3A is group 13 all the way to group 18 for group 8A. So just remember, if you're looking at the full out periodic table that I talked about in earlier chapters, you'll know that the transition metals are also represented as groups 3:00 to 12:00, and that new group number designation is also equal to the number of valence electrons.

So just remember you can do it the long way where you give the electron configurations of each transition metal and look up the number of total S in D electrons. Or you can just remember that the transition metals are represented as groups 3:00 to 12:00.

Valence Electrons of Elements Example 2

Here it says how many valence electrons with a manganese 5 ion possess. So manganese 5 means it has A5 plus or +5 charge. That means that it has lost five electrons. So remember, manganese is a transition metal. It is in Group seven of the periodic table. Don't confuse group 7 with group 7A. Group 7A are the halogens, right? But here we're talking about group 7 for this manganese ion.

So here for manganese, when it's neutral, it has seven valence electrons, but it just lost five, so we're going to subtract out five. So it should have two valence electrons left. If you wanted to do it the longer way, through the use of the electron configuration, you could also do that O. Here we need to find out what the electron configuration is of the neutral manganese. It would be Argon 4S²3D⁵.

Now remember, 5 means we would lose 5 electrons, and we lose them from the highest shell number first. So we'd lose to both of these electrons from 4S, so they'd be completely gone, and we need to lose 3 more to get to +5 charge. Those additional three would have to come from the 3D set of orbitals. So when we lose three more, we'd have left two electrons.

Remember, the number of valence electrons per transition metal is the s + d orbital electrons. We lost our 4S orbital electrons, so all we have left are these two D orbital electrons. So whether you do it the long way through the electron configuration, or if you just simply remember the secondary Grou number for the transition metals is equal to their valence electrons, you'd also find out that you have two valence electrons left. So choose the way that you're most comfortable with to get your final answer.

How many core electrons does the gallium atom possess?

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

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

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

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).