H2Se Lewis Structure in 6 Steps (With Images)

So you have seen the above image by now, right?

Let me explain the above image in short.

H2Se lewis structure has a Selenium atom (Se) at the center which is surrounded by two Hydrogen atoms (H). There are 2 single bonds between the Selenium atom (Se) and each Hydrogen atom (H). There are 2 lone pairs on the Selenium atom (Se).

If you haven’t understood anything from the above image of H2Se lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of H2Se.

So let’s move to the steps of drawing the lewis structure of H2Se.

Steps of drawing H2Se lewis structure

Step 1: Find the total valence electrons in H2Se molecule

In order to find the total valence electrons in a H2Se molecule, first of all you should know the valence electrons present in hydrogen atom as well as selenium atom.
(Valence electrons are the electrons that are present in the outermost orbit of any atom.)

Here, I’ll tell you how you can easily find the valence electrons of hydrogen as well as selenium using a periodic table.

Total valence electrons in H2Se molecule

→ Valence electrons given by hydrogen atom:

Hydrogen is group 1 element on the periodic table. ^[1] Hence the valence electron present in hydrogen is 1.

You can see that only 1 valence electron is present in the hydrogen atom as shown in the above image.

→ Valence electrons given by selenium atom:

Selenium is a group 16 element on the periodic table. ^[2] Hence the valence electrons present in selenium is 6.

You can see the 6 valence electrons present in the selenium atom as shown in the above image.

Hence, 

Total valence electrons in H2Se molecule = valence electrons given by 2 hydrogen atoms + valence electrons given by 1 selenium atom = 1(2) + 6 = 8.

Step 2: Select the central atom

For selecting the center atom, you have to remember that the atom which is less electronegative remains at the center.

(Remember: If hydrogen is present in the given molecule, then always put hydrogen outside.)

Now here the given molecule is H2Se and it contains hydrogen atoms (H) and selenium atom (Se).

You can see the electronegativity values of hydrogen atom (H) and selenium atom (Se) in the above periodic table.

If we compare the electronegativity values of hydrogen (H) and selenium (Se) then the hydrogen atom is less electronegative. But as per the rule we have to keep hydrogen outside.

So here the selenium atom (Se) is the center atom and the hydrogen atoms (H) are the outside atoms.

Step 3: Connect each atoms by putting an electron pair between them

Now in the H2Se molecule, you have to put the electron pairs between the selenium atom (Se) and hydrogen atoms (H).

This indicates that the selenium (Se) and hydrogen (H) are chemically bonded with each other in a H2Se molecule.

Step 4: Make the outer atoms stable. Place the remaining valence electrons pair on the central atom.

Now in this step, you have to check the stability of the outer atoms.

Here in the sketch of H2Se molecule, you can see that the outer atoms are hydrogen atoms.

These outer hydrogen atoms are forming a duplet and hence they are stable. 

Also, in step 1 we have calculated the total number of valence electrons present in the H2Se molecule.

The H2Se molecule has a total 8 valence electrons and out of these, only 4 valence electrons are used in the above sketch.

So the number of electrons which are left = 8 – 4 = 4.

You have to put these 4 electrons on the central selenium atom in the above sketch of H2Se molecule.

Now let’s proceed to the next step.

Step 5: Check the octet on the central atom

In this step, you have to check whether the central selenium atom (Se) is stable or not.

In order to check the stability of the central selenium (Se) atom, we have to check whether it is forming an octet or not.

You can see from the above picture that the selenium atom is forming an octet. That means it has 8 electrons.

And hence the central selenium atom is stable.

Now let’s proceed to the final step to check whether the lewis structure of H2Se is stable or not.

Step 6: Check the stability of lewis structure

Now you have come to the final step in which you have to check the stability of lewis structure of H2Se.

The stability of lewis structure can be checked by using a concept of formal charge.

In short, now you have to find the formal charge on hydrogen (H) atoms as well as selenium (Se) atom present in the H2Se molecule.

For calculating the formal charge, you have to use the following formula;

Formal charge = Valence electrons – (Bonding electrons)/2 – Nonbonding electrons

You can see the number of bonding electrons and nonbonding electrons for each atom of H2Se molecule in the image given below.

For Hydrogen (H) atom:
Valence electron = 1 (because hydrogen is in group 1)
Bonding electrons = 2
Nonbonding electrons = 0

For Selenium (Se) atom:
Valence electrons = 6 (because selenium is in group 16)
Bonding electrons = 4
Nonbonding electrons = 4

Formal charge	=	Valence electrons	–	(Bonding electrons)/2	–	Nonbonding electrons
H	=	1	–	2/2	–	0	=	0
Se	=	6	–	4/2	–	4	=	0

From the above calculations of formal charge, you can see that the hydrogen (H) atoms as well as selenium (Se) atom have a “zero” formal charge.

This indicates that the above lewis structure of H2Se is stable and there is no further change in the above structure of H2Se.

In the above lewis dot structure of H2Se, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of H2Se.

I hope you have completely understood all the above steps.

For more practice and better understanding, you can try other lewis structures listed below.

Try (or at least See) these lewis structures for better understanding:

SOCl2 Lewis Structure	ICl2- Lewis Structure
ICl5 Lewis Structure	C3H6 (Propene) Lewis Structure
NH2Cl Lewis Structure	CHO2- Lewis Structure