How To Draw Lewis Structures Five Easy Steps

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Drawing Lewis dot structures (as well known as Lewis structures or Lewis diagrams) tin be confusing, peculiarly for a beginning chemistry student. However, these structures are helpful in understanding the bonding and valence electron configurations of different atoms and molecules. The complexity of the drawing will vary depending on whether you lot are creating a Lewis dot construction for a diatomic (2-atom) covalent molecule, a larger covalent molecule, or ionically bonded molecules.

1
Write the atomic symbol for each atom. Write the 2 atomic symbols side past side. These symbols will represent the atoms present in the covalent bail. Be sure to leave enough space betwixt the atoms to describe your electrons and bonds.^[1]
- Covalent bonds share electrons and generally occur betwixt 2 nonmetals.
2
Determine the degree of the bond between the 2 atoms. Atoms can exist held together by a single, double, or triple bond. By and large, this will be dictated by the octet rule, or each cantlet'due south desire to accomplish a full valence trounce with 8 electrons (or in the example of hydrogen, 2 electrons). To determine how many electrons each atom will take, find out how many valence electrons are in the molecule, multiply that by two (each bond involves 2 electrons), and then add the number of unshared electrons.^[ii]
- For instance, O2 (oxygen gas) has six valence electrons. Multiply 6 by 2, which equals 12.
- To determine if the octet rule has been met, utilise dots to correspond the valence electrons effectually each atom. For O2, ane oxygen has 8 electrons (then the octet rule has been met), but the other has only 6 (so the octet rule has non been met). This signifies that more than than one bond is required between the ii oxygens. Therefore, 2 of the electrons are required to make a double bond between the atoms then the octet dominion is met for both.
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3
Add together your bonds to the drawing. Each bond is represented with a line betwixt the 2 atoms. For a single bail, yous would just depict 1 line from the first atom to the second. For a double or triple bail, you would depict two or 3 lines respectively.^[iii]
- For example, N2 (nitrogen gas) has a triple bail connecting the 2 nitrogen atoms. So, its bond will be notated in a Lewis diagram as 3 parallel lines connecting the two N atoms.
4
Draw unbound electrons. Some of the valence electrons in one or both of the atoms may not be involved in a bail. When this happens, you lot should represent each remaining electron with a dot around its corresponding atom. In near cases, neither atom should have more than than 8 electrons leap to information technology. You lot can bank check your work by counting each dot as 1 electron and each line equally 2 electrons.^[4]
- For example, O2 (oxygen gas) has 2 parallel lines connecting the atoms, with 2 pairs of dots (known every bit lone pairs of electrons) on each atom.
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1
Determine which atom is your central atom. This atom is unremarkably least electronegative. As such, it is virtually capable of forming bonds with many other atoms. The term 'primal cantlet' is used because all the other atoms in the molecule are bonded to this particular cantlet (just not necessarily to each other).^[v]
- Atoms like phosphorus and carbon are ofttimes fundamental atoms.
- In some more complex molecules, y'all may have multiple central atoms.
- Note that in the periodic table, electronegativity increases from left to right and decreases from summit to bottom.
two
Consider the valence electrons of the central atom. As a general (but not all-sectional) rule, atoms like to be surrounded past 8 valence electrons (the octet rule). When the central atoms bonds to the other atoms, the lowest energy configuration is one that will satisfy the octet dominion (in most cases). This can aid you determine the number of bonds that will exist between the cardinal cantlet and the other atoms considering each bail represents 2 electrons.^[vi]
- Some large atoms such as phosphorus can break the octet rule.
- For example, carbon dioxide (CO_ii) has two oxygens covalently double-bonded to the fundamental atom, carbon. This allows the octet rule to be satisfied for all 3 atoms.
- Phosphorus pentachloride (PCl₅) breaks the octet rule by having 5 bonding pairs around the central atom. This molecule has 5 chlorine atoms covalently unmarried-bonded to the key atom, phosphorus. The octet rule is satisfied for each of the 5 chlorine atoms, only information technology is exceeded for the phosphorus atom.
iii

Write the symbol of your fundamental atom. With larger covalent molecules, it is all-time to start the drawing with the central atom. Resist the urge to write all of the atomic symbols at the same time. Leave plenty of room around the primal atom to place your other symbols afterward yous have adamant their place.^[7]
iv

Show the electron geometry of the cardinal atom. For each unshared electron pair, depict 2 small dots right next to each other around the central atom. For each single bond, draw a line going abroad from the atom. For double and triple bonds, instead of 1 line, depict 2 or 3, respectively. This maps out where the other molecules can bond to the primal atom.^[8]
five

Add together remaining atoms. Each remaining atom in the molecule will attach to the one of the bonds coming from the central atom. Write the symbol for each of these atoms at the terminate of 1 of the bonds you placed around the primal cantlet. This indicates that electrons are being shared betwixt that atom and the fundamental atom.^[9]
6
Fill up in remaining electrons. Count each bond as 2 electrons (double and triple bonds as 4 and six electrons, respectively). Then add electron pairs effectually each cantlet until the octet rule is satisfied for that atom. You lot tin bank check your work on each cantlet by counting each dot as 1 electron and each bail equally 2 electrons. The sum should be 8.^[10]
- Of course, exceptions include atoms that exceed the octet rule and hydrogen, which simply has 0 or 2 valence electrons at any given time.
- When a hydrogen molecule is covalently bonded to another cantlet, it volition have no other unshared electrons surrounding information technology.
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i
Write the atomic symbol. The atomic symbol for an ion will the be the same as the atomic symbol for the cantlet that formed it. Leave enough space on the newspaper effectually the symbol to be able to add together electrons and brackets afterwards. In some cases, ions are polyatomic (more than 1 atom) molecules and are designated by writing the atomic symbol for all atoms in the molecule.^[11]
- To create the symbol for polyatomic ions (such as NO3- or SO42-), follow the instructions for "Creating Lewis Structures for Large Covalent Molecules" in the above method.
2
Fill in the electrons. Generally, atoms are neutral and practise not deport a positive or negative charge. However, when an atom loses or gains electrons, the rest of positive and negative charge in the atom is altered. And so the atom becomes a charged particle known equally an ion. On you Lewis structure, add any extra electrons and remove any electrons that were given upwards.^[12]
- When drawing the electrons, keep the octet rule in listen.
- When electrons are lost, a positive ion (known every bit a cation) is formed. For example, lithium loses its i and but valence electron during ionization. Its Lewis structure would just be 'Li' with no dots around it.
- When electrons are gained, a negative ion (known every bit an anion) is formed. Chlorine has 7 valence electrons and gains one electron during ionization, giving it a total beat of 8 electrons. Its Lewis structure would be 'Cl' with four pairs of dots around it.
three
Designate the charge of the ion. Counting dots on every atom would exist a tiresome way of determining if that atom had a charge. To make the structures easier to read, you demand to bear witness that your structure is an ion with some accuse. To prove this, draw brackets around the atomic (or polyatomic) symbol. And so, write the charge outside the brackets in the upper right corner.^[xiii]
- For example, the magnesium ion would have an empty outer beat, and would be notated as [Mg]ⁱⁱ⁺.
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Question

How do I draw the Lewis diagram for H3 O+?

Onebluethinker

Customs Answer

First notice the full number of electrons. 3x1 + 6 - ane = eight. Oxygen is the central atom, since hydrogen can simply accept two electrons and can never exist the central atom. Start by placing bonds between the oxygen atom and each of the hydrogen atoms. You accept now formed iii bonds, using up 6 electrons. The hydrogen atoms each take 2 electrons and their outer energy levels are filled. Place the last ii electrons as a lonely pair on the oxygen, and now it has eight electrons in its outer energy level.
Question

How can you know which atoms might break the octet rule?

Only atoms in the second row of the periodic table and beyond can expand their octets. Generally speaking, this happens most often when a big molecule (similar Iodine) bonds to small electronegative molecules (like oxygen or chlorine).

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The Lewis dot structures should be the same for elements in the same periodic group, though there are some exceptions.

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Article Summary 10

To draw Lewis dot structures, start by writing the diminutive symbols for the 2 atoms side-by-side. So, determine whether the atoms are held together by a single, double, or triple bond. Next, describe lines between the atoms to correspond that bail. For example, use 1 line to show a single bond, or draw 2 lines if they take a double bond. Finally, represent any remaining unbonded electrons by cartoon dots around their respective atoms. For more tips from our Science co-author, including how to make Lewis structures for larger covalent molecules or ions, read on!

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