Key principles

The electron on the outermost power level that the atom are called valence electrons.The valence electron are connected in bonding one atom to another.The attraction of each atom’s nucleus because that the valence electrons of the other atom traction the atoms together. As the attractions bring the atom together, electron from every atom are attracted to the cell core of both atoms, which “share” the electrons. The sharing of electrons between atoms is dubbed a covalent bond, i m sorry holds the atoms together as a molecule.A covalent bond happens if the attractions are strong enough in both atoms and if each atom has actually room for an electron in its outer power level.Atoms will covalently bond until their outer power level is full.Atoms covalently bonded together a molecule are an ext stable than they were as different atoms.


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


Students will have the ability to explain the attraction in between the protons and also electrons of 2 atoms cause them come bond. College student will be able to draw a design of the covalent bonds in 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 as soon as specified in the activity. The activity sheet will certainly serve as the “Evaluate” component of every 5-E great plan.


Be sure you and also the college student wear properly fitting goggles.

Materials for Each Group

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

About this lesson

This class will probably take much more than one course period.


Discuss the problems needed because that covalent bonding and also the secure molecule that is formed.

Project the image Covalent link in hydrogen.

Read more about bonding in the additional teacher background ar at the end of this lesson.

Note: This model of covalent bonding for the hydrogen molecule (H2) starts v 2 individual hydrogen atoms. In reality, hydrogen atoms are never separate to begin with. They are always bonded v something else. To simplify the process, this design does not show the hydrogen atoms breaking their bonds from other atoms. The only focuses on the process of creating covalent bonds between two hydrogen atoms.

Two hydrogen atoms are near each other.When 2 hydrogen atoms come close sufficient to every other, your electrons room attracted to the proton that the other atom.Because over there is both a strong enough attraction betweeen atoms and also room for electrons in the outer energy level of both atoms, the atoms share electrons. This develops a covalent bond.

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

There demands to it is in a strong enough attraction in between the electrons of every atom because that the protons of the various other atom. There demands to it is in room in the outer energy level of both atoms.

Once bonded, the hydrogen molecule is much more stable than the separation, personal, instance hydrogen atoms. Explain to students the by being part of a covalent bond, the electron from each hydrogen atom gets to be near two protons instead of just the one proton it began with. Due to the fact that the electrons are closer to an ext protons, the molecule of two bonded hydrogen atom is much more stable than the two individual unbonded hydrogen atoms.

This is why that is very rare to discover a hydrogen atom the is no bonded to various other atoms. Hydrogen atoms bond with other hydrogen atoms to make hydrogen gas (H2). Or they have the right to bond with various other atoms prefer oxygen to do water (H2O) or carbon to make methane (CH4) or many other atoms.

Show students that once two hydrogen atoms bond together, the outer energy level becomes full.

Have student look at their regular table of energy levels for elements 1–20 dispersed in class 3.

Explain that the 2 electrons in the hydrogen molecule (H2) have the right to be thought of together “belonging” to every atom. This way that each hydrogen atom now has two electron in its first energy level. The very first energy level in the outer energy level for hydrogen and also can just accommodate or “hold” two electrons. Atom will continue to covalently bond until their outer energy levels are full. In ~ this point, added atoms will not covalently bond to the atoms in the H2 molecule.

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

Give each college student an activity sheet.

Have students write a quick caption under each photo to describe the procedure of covalent bonding and answer the an initial three questions. The rest of the activity sheet will either it is in completed as a class, in groups, or individually, relying on your instructions.

Ask students:

What walk you create for the 2nd and 3rd pictures the covalent bonding?Center drawing: as soon as two hydrogen atoms come near enough, their electrons room attracted come the proton that the other atom. Critical drawing: This brings the atoms close enough together that they share electrons. What space two problems atoms must have actually in stimulate to type covalent bonds with one another? over there is a strong enough attraction between atoms and also there is room because that electrons in the outer power level of both atoms.Why is a hydrogen molecule (H2) more stable than two individual hydrogen atoms?In the hydrogen molecule, the electrons from every atom room able come be close to two protons rather of just the one proton it started with. Whenever an unfavorable electrons room near extr positive protons, the arrangement is an ext stable.Why doesn’t a third hydrogen atom sign up with the H2 molecule to make H3? once two hydrogen atom share your electrons v each other, your outer energy levels room full.

You can explain come students that when the outer energy levels room full, sharing electrons with another atom would certainly not happen for two main reasons:

An electron native a brand-new atom would need to join an atom in the H2 molecule ~ above the next energy level, additional from the nucleus wherein it would not feel a solid enough attraction.An electron indigenous an atom already in the H2 molecule and also close to the cell nucleus would must move additional away come share with the new atom.

Both of these possibilities would certainly make the molecule much less stable and also would not happen.

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

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

Two hydrogen atoms and also one oxygen atoms are near each other.When 2 hydrogen atom come close sufficient to an oxygen atoms, your electrons are attracted come the proton of the various other atom.Because there is both a strong enough attraction in between atoms and also room for electrons in the outer power levels the the atoms, lock share electrons. This creates a covalent bond.

Note: This design of covalent bonding because that a water molecule starts through 2 separation, personal, instance hydrogen atoms and also 1 oxygen atom. In reality, this atoms are never ever separate to begin with. Castle are always bonded with something else. To simplify the process, this version does not display the hydrogen and also oxygen atom breaking your bonds from other atoms. It only focuses on the process of creating covalent binding to make water.

Ask students:

Why can’t a third hydrogen atom join the water molecule (H20) to do H3O? once two hydrogen atoms and also an oxygen atom share their electrons v each other, their outer power levels are full.Explore

Have students use electricity to rest the covalent bond in water molecules.

Tell students that electrical energy have the right to be provided to rest the covalent bond in water molecules to produce hydrogen atoms and oxygen atoms. 2 hydrogen atoms climate bond to type hydrogen gas (H2) and two oxygen atoms bond to kind oxygen gas (O2).

You may select to perform this activity as a demonstrate or show the video Electrolysis.

Question to investigate

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

Materials because that each group

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


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

With the help of a partner, pave tape about the pencils and also battery together shown.

Add water to a clear plastic cup till it is around ½-full. Add around ½ teaspoon of Epsom salt to the water and also stir until the salt dissolves. Attach one alligator clip come one terminal of the battery.Using the other wire, connect one alligator clip come the other terminal the the battery.Connect one finish of the pencil bring about the alligator clip in ~ the end of among the wires.Using the other wire, attach one finish of the other pencil cause the alligator clip in ~ the finish of the wire.Place the end of the pencil into the water together shown.

Expected results

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

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

Discuss student observations.

Ask students:

What room the balloon made out of in the activity?Hydrogen gas (H2) and also oxygen gas (O2)Why to be there more 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 type hydrogen gas (H2) and also 2 oxygen atoms bond to form oxygen gas (O2). Each water molecule has actually all the atoms required to do 1 molecule the hydrogen gas. However with only 1 oxygen atom, a water molecule only has half of what is necessary to do 1 molecule the oxygen gas. So, 2 water molecule will produce 2 molecules of hydrogen gas yet only 1 molecule that oxygen gas.Extend

Help students understand just how atoms combine to kind the molecule of oxygen, methane, and also carbon dioxide.

Remind students the in this lesson they looked in ~ the covalent bonds in hydrogen molecules and in water molecules. Tell them that they will certainly look in ~ the covalent binding in 3 other common substances.

Project the animation Oxygen’s double bond.

Explain come students that the oxygen molecules the are current in our air are consisted of of 2 oxygen atoms. This computer animation will display them what the covalent bond in between 2 oxygen atom is like. Narrate the computer animation by stating that each oxygen atom has 6 valence electrons. As soon as the oxygen atoms get close together, the attractions indigenous the nucleus of both atoms lure the external electrons. In this case, 2 electron from each atom are shared. This is called a dual bond.

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Each oxygen atom has 6 valence electrons in its outer power levelWhen two oxygen atoms gain close to each other, the attractions indigenous the cell nucleus of both atoms attract the outer electrons.