Lewis structure of BeH2

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Lewis structure of BeH2
Lewis structure of BeH2 | Image: Root Memory

The Lewis structure of BeH2 contains two single bonds, with beryllium in the center, and two hydrogens on either side. There are no lone pairs on both the beryllium atom and hydrogen atom.

Steps

By using the following steps, you can easily draw the Lewis structure of BeH2.

#1 Draw skeleton
#2 Show chemical bond
#3 Calculate formal charge and check stability (if there are no lone pairs and octet is already completed on central atom)

Let’s one by one discuss each step in detail.

#1 Draw skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

  • Let’s calculate the total number of valence electrons

We know that… beryllium is a group 2 element and hydrogen is a group 1 element. Hence, beryllium has two valence electrons and hydrogen has one valence electron.

Now BeH2 has one beryllium atom and two hydrogen atoms.

So the total number of valence electrons = valence electrons of beryllium atom + (valence electrons of hydrogen atom × 2)

Therefore, the total number of valence electrons = 2 + 2 = 4

  • Now decide the central atom

We can not assume hydrogen as the central atom, because the central atom is bonded with at least two other atoms. And hydrogen has only one electron in its last shell, so it can not make more than one bond.

Hence, assume that beryllium is the central atom.

So now, put beryllium in the center and hydrogens on either side. And draw the rough skeleton structure for the Lewis structure of BeH2 something like this:

Skeleton structure for Lewis structure of BeH2 | Image: Root Memory

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since beryllium is surrounded by two hydrogens, use four electrons to show two chemical bonds as follows:

Two chemical bonds shown between atoms | Image: Root Memory

In the above structure, you can see that the octet is completed on outside atoms. But, the central atom (beryllium) doesn’t form an octet.

Now beryllium has an exception in BeH2, that it does not require eight electrons to complete its octet.

So one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

#3 Calculate formal charge and check stability

The following formula is used to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

Collect the data from the above structure and then, write it down below as follows:

  • For beryllium atom

Valence electrons = 2
Nonbonding electrons = 0
Bonding electrons = 4

Formal charge = 2 – 0 – ½ (4) = 0

  • For each hydrogen atom

Valence electrons = 1
Nonbonding electrons = 0
Bonding electrons = 2

Formal charge = 1 – 0 – ½ (2) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of BeH2 looks something like this:

Formal charges are calculated, and got the stable Lewis structure of BeH2 | Image: Root Memory

In the above structure, you can see that the formal charges of both (beryllium and hydrogen) are zero. Therefore, this is the stable Lewis structure of BeH2.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

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Deep

Rootmemory.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.

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