how to draw lewis dot structure

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Drawing Lewis dot structures (also known every bit Lewis structures or Lewis diagrams) can be confusing, particularly for a first chemical science student. However, these structures are helpful in understanding the bonding and valence electron configurations of different atoms and molecules. The complication of the drawing will vary depending on whether you lot are creating a Lewis dot structure for a diatomic (two-atom) covalent molecule, a larger covalent molecule, or ionically bonded molecules.

1
Write the atomic symbol for each atom. Write the ii atomic symbols next. These symbols volition represent the atoms nowadays in the covalent bond. Exist certain to get out plenty space between the atoms to draw your electrons and bonds.^[one]
- Covalent bonds share electrons and generally occur betwixt two nonmetals.
two
Make up one's mind the degree of the bond between the two atoms. Atoms can be held together by a single, double, or triple bond. Generally, this volition exist dictated by the octet rule, or each atom'south desire to reach a total valence shell with 8 electrons (or in the example of hydrogen, two electrons). To determine how many electrons each atom will have, discover out how many valence electrons are in the molecule, multiply that by two (each bond involves ii electrons), and and so add together the number of unshared electrons.^[2]
- For instance, O2 (oxygen gas) has 6 valence electrons. Multiply half dozen past 2, which equals 12.
- To decide if the octet rule has been met, use dots to stand for the valence electrons around each atom. For O2, 1 oxygen has viii electrons (so the octet rule has been met), only the other has simply half-dozen (so the octet dominion has not been met). This signifies that more than 1 bail is required between the 2 oxygens. Therefore, ii of the electrons are required to make a double bond between the atoms so the octet rule is met for both.
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Add together your bonds to the drawing. Each bond is represented with a line between the 2 atoms. For a single bond, you would but draw 1 line from the first atom to the 2nd. For a double or triple bond, you would draw 2 or 3 lines respectively.^[3]
- For example, N2 (nitrogen gas) has a triple bond connecting the ii nitrogen atoms. So, its bond will be notated in a Lewis diagram every bit 3 parallel lines connecting the two Due north atoms.
iv
Describe unbound electrons. Some of the valence electrons in 1 or both of the atoms may not be involved in a bail. When this happens, you should represent each remaining electron with a dot around its respective atom. In most cases, neither atom should have more than than eight electrons jump to it. You can cheque your piece of work by counting each dot as i electron and each line equally 2 electrons.^[4]
- For instance, O2 (oxygen gas) has 2 parallel lines connecting the atoms, with 2 pairs of dots (known as lone pairs of electrons) on each atom.
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1
Determine which atom is your primal atom. This atom is unremarkably least electronegative. Every bit such, information technology is almost capable of forming bonds with many other atoms. The term 'fundamental atom' is used because all the other atoms in the molecule are bonded to this detail atom (merely non necessarily to each other).^[v]
- Atoms like phosphorus and carbon are frequently central atoms.
- In some more than complex molecules, you may accept multiple cardinal atoms.
- Annotation that in the periodic table, electronegativity increases from left to right and decreases from top to bottom.
2
Consider the valence electrons of the cardinal cantlet. As a general (only not all-exclusive) rule, atoms like to be surrounded by 8 valence electrons (the octet dominion). When the central atoms bonds to the other atoms, the lowest energy configuration is i that will satisfy the octet rule (in near cases). This can aid you decide the number of bonds that will be between the central cantlet and the other atoms because each bond represents 2 electrons.^[6]
- Some large atoms such as phosphorus can break the octet dominion.
- For example, carbon dioxide (CO₂) has 2 oxygens covalently double-bonded to the primal atom, carbon. This allows the octet rule to be satisfied for all 3 atoms.
- Phosphorus pentachloride (PCl₅) breaks the octet rule by having v bonding pairs around the cardinal atom. This molecule has five chlorine atoms covalently unmarried-bonded to the central cantlet, phosphorus. The octet rule is satisfied for each of the 5 chlorine atoms, but it is exceeded for the phosphorus atom.
iii

Write the symbol of your central atom. With larger covalent molecules, it is all-time to outset the drawing with the cardinal atom. Resist the urge to write all of the atomic symbols at the same fourth dimension. Leave enough of room around the central atom to place your other symbols after y'all have determined their identify.^[seven]
4

Show the electron geometry of the central atom. For each unshared electron pair, depict 2 small dots right adjacent to each other around the central cantlet. For each single bail, draw a line going abroad from the cantlet. For double and triple bonds, instead of 1 line, draw 2 or 3, respectively. This maps out where the other molecules can bond to the cardinal atom.^[viii]
5

Add together remaining atoms. Each remaining atom in the molecule volition adhere to the one of the bonds coming from the central atom. Write the symbol for each of these atoms at the end of ane of the bonds you placed around the central atom. This indicates that electrons are beingness shared between that atom and the central atom.^[9]
six
Fill in remaining electrons. Count each bond as 2 electrons (double and triple bonds every bit 4 and 6 electrons, respectively). Then add together electron pairs around each cantlet until the octet rule is satisfied for that atom. You lot tin check your work on each atom by counting each dot equally 1 electron and each bond as 2 electrons. The sum should be viii.^[10]
- Of course, exceptions include atoms that exceed the octet rule and hydrogen, which only has 0 or 2 valence electrons at any given fourth dimension.
- When a hydrogen molecule is covalently bonded to another atom, it will have no other unshared electrons surrounding information technology.
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1
Write the diminutive symbol. The atomic symbol for an ion will the be the same every bit the atomic symbol for the atom that formed it. Get out plenty infinite on the newspaper around the symbol to be able to add electrons and brackets later. In some cases, ions are polyatomic (more than 1 atom) molecules and are designated past 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.
ii
Fill in the electrons. Generally, atoms are neutral and do not conduct a positive or negative charge. However, when an cantlet loses or gains electrons, the balance of positive and negative charge in the atom is altered. And then the atom becomes a charged particle known as an ion. On you Lewis construction, add any extra electrons and remove any electrons that were given up.^[12]
- When drawing the electrons, go along the octet rule in listen.
- When electrons are lost, a positive ion (known equally a cation) is formed. For example, lithium loses its one and merely valence electron during ionization. Its Lewis structure would just be 'Li' with no dots effectually information technology.
- When electrons are gained, a negative ion (known as an anion) is formed. Chlorine has 7 valence electrons and gains 1 electron during ionization, giving it a full shell of eight electrons. Its Lewis construction would be 'Cl' with 4 pairs of dots around information technology.
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Designate the charge of the ion. Counting dots on every atom would be a dull fashion of determining if that atom had a accuse. To make the structures easier to read, you need to testify that your construction is an ion with some charge. To bear witness this, draw brackets around the atomic (or polyatomic) symbol. Then, write the charge exterior the brackets in the upper correct corner.^[13]
- For example, the magnesium ion would accept an empty outer shell, and would be notated as [Mg]ⁱⁱ⁺.
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Question

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

Onebluethinker

Community Answer

First detect the total number of electrons. 3x1 + 6 - i = 8. Oxygen is the central atom, since hydrogen tin can only have 2 electrons and can never be the central atom. Start by placing bonds between the oxygen atom and each of the hydrogen atoms. Yous have at present formed 3 bonds, using upwards 6 electrons. The hydrogen atoms each have ii electrons and their outer energy levels are filled. Place the last 2 electrons as a alone pair on the oxygen, and now information technology has 8 electrons in its outer energy level.
Question

How tin can you lot know which atoms might intermission the octet dominion?

Just atoms in the 2nd row of the periodic table and across can expand their octets. Generally speaking, this happens almost frequently when a large molecule (like Iodine) bonds to minor 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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Commodity Summary X

To draw Lewis dot structures, start by writing the diminutive symbols for the 2 atoms side-by-side. Then, determine whether the atoms are held together by a single, double, or triple bail. Next, draw lines between the atoms to correspond that bail. For example, utilize 1 line to show a single bond, or draw 2 lines if they have a double bond. Finally, represent any remaining unbonded electrons by drawing 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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