Key ideas

The electrons on the outermost power level the the atom are dubbed valence electrons.The valence electrons are connected in bonding one atom to another.The attraction of every atom’s nucleus because that the valence electron of the various other atom pulls the atoms together. As the attractions bring the atom together, electrons from each atom space attracted come the cell core of both atoms, i beg your pardon “share” the electrons. The share of electrons in between atoms is referred to as a covalent bond, i beg your pardon holds the atoms together as a molecule.A covalent bond happens if the attractions are strong enough in both atoms and also if each atom has room for an electron in that is outer energy level.Atoms will certainly covalently bond until their outer energy level is full.Atoms covalently bonded as a molecule are more stable than they to be as different atoms.


Students will certainly look in ~ animations and also refer come the energy level models they have been making use of to make drawings of the procedure of covalent bonding. Students will consider why atom bond to type molecules favor H2 (hydrogen), H2O (water), O2 (oxygen), CH4 (methane), and CO2 (carbon dioxide).


Students will have the ability to explain the attraction between the protons and also electrons of 2 atoms reason them to bond. Student will be able to draw a design of the covalent bonds between the atoms in H2 (hydrogen), H2O (water), O2 (oxygen), CH4 (methane), and CO2 (carbon dioxide).

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Download the student activity sheet, and also distribute one per student once specified in the activity. The task sheet will serve as the “Evaluate” component of every 5-E class plan.


Be sure you and the students wear correctly fitting goggles.

Materials for Each Group

9-volt battery2 wires with alligator clips on both ends2 pencils sharpened in ~ both endsWaterSaltClear plastic cupTape

About this lesson

This lesson will more than likely take more than one class period.


Discuss the conditions needed because that covalent bonding and also the steady molecule that is formed.

Project the image Covalent link in hydrogen.

Read an ext about bonding in the extr teacher background section at the end of this lesson.

Note: This design of covalent bonding because that the hydrogen molecule (H2) starts with 2 separation, personal, instance hydrogen atoms. In reality, hydrogen atom are never ever separate to start with. They are constantly bonded with something else. To simplify the process, this model does not display the hydrogen atoms breaking their bonds from other atoms. It only concentrates on the process of developing covalent bonds in between two hydrogen atoms.

Two hydrogen atoms are near each other.When two hydrogen atoms come close sufficient to every other, your electrons space attracted come the proton that the other atom.Because over there is both a solid enough attraction betweeen atoms and also room because that electrons in the outer power level that both atoms, the atom share electrons. This forms a covalent bond.

Tell students the there room two main reasons why 2 hydrogen atoms bond together to do one hydrogen molecule:

There requirements to it is in a strong enough attraction between the electrons of every atom for the protons of the other atom. There needs to be room in the outer power level that both atoms.

Once bonded, the hydrogen molecule is much more stable 보다 the separation, personal, instance hydrogen atoms. Explain to students that by being part of a covalent bond, the electron from each hydrogen atom gets to be close to two protons rather of only the one proton it began with. Because the electrons space closer to an ext protons, the molecule of 2 bonded hydrogen atoms is more stable than the 2 individual unbonded hydrogen atoms.

This is why it is really rare to find a hydrogen atom that is not bonded to other atoms. Hydrogen atoms bond with other hydrogen atoms to do hydrogen gas (H2). Or they deserve to bond with various other atoms like oxygen to do water (H2O) or carbon to do methane (CH4) or plenty of other atoms.

Show student that as soon as two hydrogen atom bond together, the outer energy level becomes full.

Have students look in ~ their periodic table of energy levels for elements 1–20 distributed in lesson 3.

Explain that the two electrons in the hydrogen molecule (H2) have the right to be assumed of together “belonging” to each atom. This method that each hydrogen atom now has two electrons in its first energy level. The first energy level in the outer power level for hydrogen and also can only accommodate or “hold” two electrons. Atom will proceed to covalently bond till their outer energy levels room full. At this point, added atoms will certainly not covalently bond come the atoms in the H2 molecule.

Have students explain covalent bonding in a hydrogen molecule top top their activity sheet and also then evaluation their answers.

Give each student an activity sheet.

Have students compose a quick caption under each photo to define the procedure of covalent bonding and also answer the first three questions. The rest of the task sheet will either be completed as a class, in groups, or individually, depending upon your instructions.

Ask students:

What did you compose for the 2nd and 3rd pictures the covalent bonding?Center drawing: once two hydrogen atom come near enough, their electrons room attracted come the proton of the various other atom. Last drawing: This brings the atoms close sufficient together that they re-superstructure electrons. What room two problems atoms must have in stimulate to type covalent bonds v one another? there is a solid enough attraction between atoms and also there is room for electrons in the outer power level that both atoms.Why is a hydrogen molecule (H2) an ext stable than 2 individual hydrogen atoms?In the hydrogen molecule, the electrons from each atom are able to be near two protons instead of only the one proton it began with. Whenever negative electrons room near added positive protons, the setup is an ext stable.Why doesn’t a 3rd hydrogen atom sign up with the H2 molecule to do H3? when two hydrogen atoms share your electrons through each other, your outer energy levels are full.

You can explain come students that as soon as the outer power levels are full, share electrons with an additional atom would certainly not happen for two key reasons:

An electron from a new atom would need to join an atom in the H2 molecule on the next power level, more from the nucleus wherein it would certainly not feeling a strong enough attraction.An electron native an atom already in the H2 molecule and close come the cell core would must move further away to share v the new atom.

Both of these possibilities would certainly make the molecule much less stable and also would no happen.

Have students define covalent bonding in a water molecule on their task sheet.

Have students create a short caption alongside each snapshot to explain the procedure of covalent bonding in the water molecule.

Two hydrogen atoms and also one oxygen atom are near each other.When two hydrogen atoms come close enough to an oxygen atoms, their electrons are attracted come the proton that the various other atom.Because there is both a solid enough attraction in between atoms and room because that electrons in the outer energy levels the the atoms, castle share electrons. This forms a covalent bond.

Note: This design of covalent bonding for a water molecule starts through 2 individual hydrogen atoms and 1 oxygen atom. In reality, these atoms are never ever separate to begin with. Castle are always bonded v something else. To leveling the process, this version does not display the hydrogen and also oxygen atom breaking their bonds from other atoms. It only concentrates on the process of developing covalent binding to make water.

Ask students:

Why can’t a 3rd hydrogen atom sign up with the water molecule (H20) to do H3O? once two hydrogen atoms and also an oxygen atom share your electrons through each other, their outer power levels space full.Explore

Have student use electrical power to rest the covalent binding in water molecules.

Tell college student that electrical energy deserve to be supplied to rest the covalent bond in water molecule to develop hydrogen atoms and also oxygen atoms. Two hydrogen atoms climate bond to form hydrogen gas (H2) and also two oxygen atoms bond to type oxygen gas (O2).

You may pick to carry out this activity as a demonstrate or show the video Electrolysis.

Question to investigate

What is created when the covalent bond in water molecules is broken?

Materials because that each group

9-volt battery2 wires with alligator clips on both ends2 pencils sharpened at both endsWaterEpsom salt (magnesium sulfate)Clear plastic cupTape


Place a battery between 2 pencils. Be certain that the battery is much more than half-way up.

With the aid of a partner, wrap tape about the pencils and also battery together shown.

Add water to a clean plastic cup until it is about ½-full. Add around ½ teaspoon of Epsom salt come the water and also stir till the salt dissolves. Connect one alligator clip come one terminal the the battery.Using the various other wire, affix one alligator clip to the various other terminal the the battery.Connect one end of the pencil lead to the alligator clip in ~ the finish of one of the wires.Using the other wire, affix one end of the various other pencil bring about the alligator clip at the finish of the wire.Place the ends of the pencil into the water together shown.

Expected results

Bubbles will form and rise at first from one pencil lead. Soon, bubbles will type and climb from the other. College student should be able to see that there is much more of one gas 보다 the other. The gas that forms the little bubbles that comes off an initial is hydrogen. The other gas that forms the bigger bubbles and also lags behind a little is oxygen.

Note: There will certainly be bubbling when hydrogen and oxygen gas form on the pencil leads. Be sure students do not acquire the misconception that the bubbles they see average that the water is boiling. In boiling, the bond holding the atoms with each other in water molecules perform not come apart. In the process of electrolysis, the bonds holding the atoms together perform come apart.

Discuss student observations.

Ask students:

What space the bubbles made out of in the activity?Hydrogen gas (H2) and also oxygen gas (O2)Why to be there an ext hydrogen gas created than oxygen gas?Each water molecule breaks right into 2 hydrogen atoms and 1 oxygen atom. 2 hydrogen atoms climate bond to kind hydrogen gas (H2) and 2 oxygen atoms bond to form oxygen gas (O2). Every water molecule has actually all the atoms needed to make 1 molecule the hydrogen gas. Yet with only 1 oxygen atom, a water molecule only has fifty percent of what is essential to do 1 molecule the oxygen gas. So, 2 water molecules will create 2 molecule of hydrogen gas however only 1 molecule that oxygen gas.Extend

Help students understand just how atoms integrate to form the molecules of oxygen, methane, and also carbon dioxide.

Remind students the in this lesson castle looked in ~ the covalent bonds in hydrogen molecules and also in water molecules. Call them the they will certainly look at the covalent bonds in three other typical substances.

Project the computer animation Oxygen’s double bond.

Explain to students the the oxygen molecules that are current in ours air are made up of 2 oxygen atoms. This computer animation will display them what the covalent bond in between 2 oxygen atom is like. Narrate the animation by stating that each oxygen atom has 6 valence electrons. Once the oxygen atoms get close together, the attractions from the nucleus of both atoms attract the external electrons. In this case, 2 electrons from each atom room shared. This is called a double bond.

See more: The Energy Released In This Process Was Originally Present In

Each oxygen atom has actually 6 valence electrons in the outer power levelWhen 2 oxygen atoms obtain close to each other, the attractions indigenous the cell nucleus of both atoms entice the external electrons.