Valence electrons are kind of like the directions to a Lego set. In this lesson, we will learn what valence electrons are and why scientists need to know the number of valence electrons an atom has.
The Combining Game
Have you ever taken two different things and combined them to make something brand new? Maybe you have taken two or more completely different Lego sets and put all the pieces together and invented something. Maybe you've helped your parents cook in the kitchen and combined many different ingredients and came out with cookies. Yum!
Scientists do this with elements in the periodic table to make new substances. They cannot just combine elements at random, though. Elements are very picky about what they combine with. However, they give scientists a clue of what other element they might combine with. That clue is the element's number of valence electrons.
What Is a Valence Electron?
You may already know that an electron is a negatively charged particle of an atom. A valence electron is an electron that 'lives' in the last electron shell (or valence shell) of an atom. The atom will have one or more electron shells based on how many electrons the atom has. The very last shell that the atom has holds the valence electrons. The number of valence electrons that an atom has tells us what it might be able to combine with to make something new.
Finding out the number of valence electrons an atom has may sound impossible. Scientists have organized the periodic table to make it easy to determine the number of electrons that an atom has. By looking at the group number that an element is in, we can determine the valence electrons that the atom of that element has. The number in the ones place of the group number is equal to the number of valence electrons in that atom (i.e. group 1 elements have 1 valence electron, group 16 elements have 6 valence electrons).
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The only time that this does not work is with the transition metals (groups 3-12 of the periodic table). They are a rebellious group and do not follow the same rules as all of the other groups on the periodic table. Some elements in this group can combine in many different configurations making it very hard to determine valence electrons.
Why This Is Important
All atoms have one goal: they want to have eight valence electrons. Scientists can use this to determine which elements will easily combine with other elements. For example, an element from group 1 needs 7 more electrons. An element from group 7 needs 1 more electron. Elements from group 1 and 7 will easily combine together, because then they will have 8 valence electrons.
Okay, let's review what we've learned in this lesson on valence electrons and how they work. Valence electrons are the electrons in the last electron shell of an atom. Remember that an electron is a negatively charged particle that orbits the atom. They're important to scientists to help them determine what elements might combine together to form new substances. The periodic table will help us determine the number of valence electrons that an atom of a substance has based on what group that element is found in. Groups 3-12 are rebellious and don't follow these rules. All atoms want to have a full valence electron shell. Their goal is to have 8 valence electrons.
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