1. Is Sodium Diatomic
2. Helium Is Diatomic Molecule

This is the SUPER easy guide on Helium element.

• A brief discussion on bonding in homonuclear diatomic molecules like dihydrogen, lithium, oxygen, carbon, helium and more. Learn more about diatomic molecules and homonuclear diatomic with Byju's.
• Helium, chemical element, inert gas of Group 18 (noble gases) of the periodic table. The second lightest element, helium is a colorless, odorless, and tasteless gas that becomes liquid at -268.9 degrees Celsius. The boiling and freezing points of helium are lower than those of any other known substance.
• Diatomic molecules are composed of only two atoms, of either the same or different chemical elements. Common diatomic molecules include hydrogen (H 2), nitrogen (N 2), oxygen (O 2), and carbon monoxide (CO).Seven elements exist as homonuclear diatomic molecules at room temperature: H 2, N 2, O 2, F 2, Cl 2, Br 2, and I 2.The bond in a homonuclear diatomic molecule is non-polar due to the.

Helium atom do not require any other electrons for its stability. Due to this stable configuration, the single atoms of helium are highly stable, and so helium exists as monatomic He and not as diatomic He 2. 6 Interesting Facts about Helium element The facts about helium element are mentioned below. Helium is a noble gas, so it is stable and does not need to bond with anything. I think there are 7 diatomics, hydrogen and some halogens?? Not positive on that. Its just a short list that you.

In fact, the table mentioned below is the perfect information box (Which gives you every single detail about the Helium element in Periodic table.)

So if you want to know anything about Helium element, then this guide is for you.

Let’s finish this very quickly.

Helium Element (He) Information

Helium in Periodic table

Helium element is in period 1 and group 18 of the Periodic table. Helium is the p-block element and it belongs to the Noble gases group.

Why is Helium not in Group 2?

Do you know how many valence electrons helium has?

It has 2 valence electrons.

So it should be placed in group 2 of the Periodic table, but in reality it is not so.

It is placed in group 18 instead of placing it in group 2.

Why?

Let me explain to you the reasons why helium is not in Group 2 and why it is in group 18.

Is Sodium Diatomic

Helium is the element which has 2 electrons only, and these two electrons are nothing but they are the valence electrons.

Helium element is very happy and stable with these two electrons.

(Note: Generally for all the elements, octet is the stable configuration. But helium is the only exception in which duplet configuration is stable.)

Helium shows the very similar physical and chemical properties as that of the group 18 elements.
Helium element do not react with other elements and hence it is chemically inert.
As helium has the same properties (like that of neon, argon, krypton, xenon and radon), it is placed along with these elements (in group 18) and not in group 2.

I hope you have clearly understood the reason why helium is not in Group 2.

Why is Helium in Period 1?

First of all let me ask you a simple question.

How many shells or orbits does the helium element have?

It’s only one, right?

You have already seen the Bohr model of Helium atom in the above table. It has only one shell.

And the number of shells indicates the position of elements in the period.

Hence, as Helium has 1 shell, it lies in period 1.

Why is Helium in p-block?

Before knowing this reason, first of all a simple question to you.

How can you determine the blocks wise position of elements?

The simple answer: The elements will lie in the s, p, d or f block will completely depend upon the subshell in which the last electron will enter.

For example; the electron configuration of Helium is 1s².

So the last electron of helium enters the s-subshell or s-orbital.

Hence, helium should be placed in the s-block of Periodic table.

But it is not so. On the modern periodic table, helium is placed in the p-block instead of s-block.

This is because Helium shows similar properties as that of Noble gases.

As its properties are similar to the Noble gases, it is placed along with them in group 18 in p-block.

Is Helium explosive?

No.

Helium does not explode when it is subjected to fire.

There are many misconceptions regarding the explosion of helium gas.

You might have heard about the explosion of helium gas balloons.

But the fact is that it is not helium gas which is filled in the balloons.

The balloons which catch fire are the hydrogen gas balloons (not the helium gas balloons.)

Helium is a non explosive gas.

Helium is chemically inert gas and so it does not react with any other elements.

But sometimes the explosion of helium tanks may occur.

Why?

The reason is mechanical failure of the tank due to high pressure.

The helium tank is filled in the tank with a high pressure.

The pressure is so high that the helium gas becomes liquid inside the cylinder.

For storing the gas at such high pressure, the tanks must resist the high pressure of the gas.

If the tank is corroded or if it is non resistive to the high pressure, then there are chances of explosion of the cylinder.

Finally, I want to tell you that Helium gas is non reactive and non explosive. That means if you put an ignited matchstick near the pure helium gas, then it will not explode.

But sometimes explosion of helium tank occur due to mechanical failure, and not because of the chemical properties of the helium.

I hope this is now clear to you.

Why is Helium the Smallest atom?

Helium is the smallest atom with the atomic radius 140 picometer (van der Waals radius).

But the question is, why is helium the smallest atom?

You can understand the reason behind the smaller size of helium atom from the following two concepts.

1. Periodic trends
2. Effective nuclear charge

I’ll explain these two concepts in just few seconds. But first of all you should have some basic knowledge about Trends in Periodic table.

Trends are the changes in properties of elements across the period (from left to right) and down the group (from top to bottom) in the Periodic table.

Let’s come to the main point.

Here we want to know about the size of helium atom.

So the important question is;

What is the atomic size trend in the Periodic table?

The simple answer: Atomic size increases down the group (from top to bottom) and it decreases across the period (from left to right).

Now the helium atom is located at the far top-right side of the Periodic table.

So according to the Periodic trends, the size of helium atom is the smallest in entire Periodic table.

Now, let me explain the concept in another way.

As we move from left to right in the Periodic table, the effective nuclear charge increases.

Means the number of positively charged protons increases, which attracts the surrounding electrons with a greater force of attraction.

In simple words, the power of nucleus to pull the electrons towards itself will increase.

Now, helium has only one shell and it is also located at the right most column. So it’s electrons will be more attracted towards the nucleus.

Hence due to the attractive force towards the nucleus, the size of helium atoms shrinks.

Hence it is the smallest atom in the Periodic table.

Why is Helium a Noble Gas?

Helium is a noble gas because it has completely filled outermost orbit.

The outermost orbit of helium atom has 2 electrons and it shows a stable duplet configuration.

In other words, the electron configuration of helium element is 1s².

It has completely filled s-orbitals and it is stable.

Because of this stable configuration, it does not react with any other elements.

Hence, as the helium gas is chemically inert, it is called noble gas.

Also see:List and electronic configuration of Noble gases.

Is Helium Monatomic or Diatomic?

Helium is Monatomic.

Let me explain to you the reason behind this.

Helium has a stable duplet configuration.

In other words, it has two electrons in the outer shell and they are completely stable.

Helium atom do not require any other electrons for its stability.

Due to this stable configuration, the single atoms of helium are highly stable, and so helium exists as monatomic He and not as diatomic He₂.

6 Interesting Facts about Helium element

The facts about helium element are mentioned below;

• Helium was first discovered in the Sun’s atmosphere (And not in Earth’s atmosphere.)
• Helium is very very lighter than air. So it always escapes the earth atmosphere and it goes into space.
• At absolute zero temperature, the helium gas becomes liquid and it shows the properties of superfluid.
• Helium is the second most abundant element found in the Universe and it makes roughly up to 24% of it. (Note: Hydrogen is first and it is roughly 74% of all the elements in the universe)
• On the earth, helium is obtained from the decay of radioactive elements like uranium and thorium.
• Helium atom is the smallest atom out of all the known elements.

Bonus Gift for you: Interactive Periodic Table

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1). You can effortlessly find every single detail about the elements from this single Interactive Periodic table.

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References
Element data: Wikipedia, Chemspider.
Pierre Jules César Janssen: Image from Public domain, via Wikimedia Commons
Sir Joseph Norman Lockyer: Image by Stereoscopic Co., Public domain, via Wikimedia Commons
Helium dewer: Image by Zureks, CC BY-SA 3.0, via Wikimedia Commons

Diatomic Elements: Diatomic molecules are molecules composed of only two atoms, of the same or different chemical elements. The prefix di- is of Greek origin, meaning “two”. If a diatomic molecule consists of two atoms of the same element, such as hydrogen (H₂) or oxygen (O₂), then it is said to be homonuclear. Otherwise, if a diatomic molecule consists of two different atoms, such as carbon monoxide (CO) or nitric oxide (NO), the molecule is said to be heteronuclear. The bond in a homonuclear diatomic molecule is non-polar.

The only chemical elements that form stable homonuclear diatomic molecules at standard temperature and pressure (STP) (or typical laboratory conditions of 1 bar and 25 °C) are the gases hydrogen (H₂), nitrogen (N₂), oxygen (O₂), fluorine (F₂), and chlorine (Cl₂).

The noble gases (helium, neon, argon, krypton, xenon, and radon) are also gases at STP, but they are monatomic. The homonuclear diatomic gases and noble gases together are called “elemental gases” or “molecular gases”, to distinguish them from other gases that are chemical compounds.

At slightly elevated temperatures, the halogens bromine (Br₂) and iodine (I₂) also form diatomic gases. All halogens have been observed as diatomic molecules, except for astatine, which is uncertain.

The mnemonics BrINClHOF, pronounced “Brinklehof”, and HONClBrIF, pronounced “Honkelbrif”, and HOFBrINCl (pronounced as Hofbrinkle) have been coined to aid recall of the list of diatomic elements.

What are the 8 diatomic elements?

The elements found as diatomic molecules are hydrogen (H, element 1), nitrogen (N, element 7), oxygen (O, element 8), fluorine (F, element 9), chlorine (Cl, element 17), bromine (Br, element 35), and iodine (I, element 53).

7 Diatomic Elements

This is a list of the seven diatomic elements. The seven diatomic elements are:

• Hydrogen (H2)
• Nitrogen (N2)
• Oxygen (O2)
• Fluorine (F2)
• Chlorine (Cl2)
• Iodine (I2)
• Bromine (Br2)

All of these elements are nonmetals, since the halogens are a special type of nonmetallic element. Bromine is a liquid at room temperature, while the other elements all gases under ordinary conditions. As the temperature is lowered or pressure is increased, the other elements become diatomic liquids.

Astatine (atomic number 85, symbol At) and tennessine (atomic number 117, symbol Ts) are also in the halogen group and may form diatomic molecules. However, some scientists predict tennessine may behave more like a noble gas.

What Are The Diatomic Elements

Diatomic elements played an important role in the elucidation of the concepts of element, atom, and molecule in the 19th century, because some of the most common elements, such as hydrogen, oxygen, and nitrogen, occur as diatomic molecules. John Dalton’s original atomic hypothesis assumed that all elements were monatomic and that the atoms in compounds would normally have the simplest atomic ratios with respect to one another. For example, Dalton assumed water’s formula to be HO, giving the atomic weight of oxygen as eight times that of hydrogen, instead of the modern value of about 16. As a consequence, confusion existed regarding atomic weights and molecular formulas for about half a century.

As early as 1805, Gay-Lussac and von Humboldt showed that water is formed of two volumes of hydrogen and one volume of oxygen, and by 1811 Amedeo Avogadro had arrived at the correct interpretation of water’s composition, based on what is now called Avogadro’s law and the assumption of diatomic elemental molecules. However, these results were mostly ignored until 1860, partly due to the belief that atoms of one element would have no chemical affinity toward atoms of the same element, and also partly due to apparent exceptions to Avogadro’s law that were not explained until later in terms of dissociating molecules.

At the 1860 Karlsruhe Congress on atomic weights, Cannizzaro resurrected Avogadro’s ideas and used them to produce a consistent table of atomic weights, which mostly agree with modern values. These weights were an important prerequisite for the discovery of the periodic law by Dmitri Mendeleev and Lothar Meyer.

Diatomic Elements List

A diatomic element is a molecule of an element consisting of two atoms. It is a form of homonuclear diatomic molecule. There are only 7 diatomic elements in total and only 5 diatomic elements at standard temperature and pressure (STP).

The following 5 element gases are found as diatomic molecules at room temperature and pressure:

• Hydrogen – H₂
• Nitrogen – N₂
• Oxygen – O₂
• Fluorine – F₂
• Chlorine – Cl₂

Bromine and iodine commonly exist in liquid form, but also as diatomic gases at slightly higher temperatures, making a total of 7 diatomic elements.

• Bromine – Br₂
• Iodine – I₂

How To Remember the Diatomic Elements

An easy mnemonic device is:

Have No Fear Of Ice Cold Beer

Hydrogen
Nitrogen
Fluorine
Oxygen
Iodine
Chlorine
Bromine

The diatomic elements are the –ine halogens (fluorine, chlorine, bromine, iodine) and elements with a –gen ending (hydrogen, oxygen, nitrogen). Astatine is another halogen, but its behavior is not known.

What Are Diatomic Elements

Diatomic molecules are normally in their lowest or ground state, which conventionally is also known as the {displaystyle X} state. When a gas of diatomic molecules is bombarded by energetic electrons, some of the molecules may be excited to higher electronic states, as occurs, for example, in the natural aurora; high-altitude nuclear explosions; and rocket-borne electron gun experiments. Such excitation can also occur when the gas absorbs light or other electromagnetic radiation. The excited states are unstable and naturally relax back to the ground state. Over various short time scales after the excitation (typically a fraction of a second, or sometimes longer than a second if the excited state is metastable), transitions occur from higher to lower electronic states and ultimately to the ground state, and in each transition results a photon is emitted. This emission is known as fluorescence. Successively higher electronic states are conventionally named {displaystyle A}, {displaystyle B}, {displaystyle C}, etc. (but this convention is not always followed, and sometimes lower case letters and alphabetically out-of-sequence letters are used, as in the example given below). The excitation energy must be greater than or equal to the energy of the electronic state in order for the excitation to occur.

In quantum theory, an electronic state of a diatomic molecule is represented by the molecular term symbol

{displaystyle ^{2S+1}Lambda (v)}

where {displaystyle S} is the total electronic spin quantum number, {displaystyle Lambda } is the total electronic angular momentum quantum number along the internuclear axis, and {displaystyle v} is the vibrational quantum number. {displaystyle Lambda } takes on values 0, 1, 2, …, which are represented by the electronic state symbols {displaystyle Sigma }, {displaystyle Pi }, {displaystyle Delta },…. For example, the following table lists the common electronic states (without vibrational quantum numbers) along with the energy of the lowest vibrational level ({displaystyle v=0}) of diatomic nitrogen (N₂), the most abundant gas in the Earth’s atmosphere. In the table, the subscripts and superscripts after {displaystyle Lambda } give additional quantum mechanical details about the electronic state.

All Diatomic Elements

Something in the way you ask makes me think you are referring to “Diatomic Homonuclear molecules”, a.k.a -non officially- Diatomic Elements.

Helium Is Diatomic Molecule

Well, some elements are more stable combined with atoms of the same type than alone. So they “prefer” to be attached to another atom of the same element.

Individual atoms are quite reactive because of their incomplete valence shells and by their closeness to their correspondent noble gases. We can say that those atoms really want to complete his shells and that translates in their high electronegativy.

Why? Its just the way nature works. But as we scientists hate empirical answers, I´ll give you additional data, even if they’re no is a Ultimate Why.

*Firs, let’s remember which of all elements are as you call, diatomic:

The fact that these elements are diatomic is ONLY when they are alone, NOT when chemically bonded to another atom. When hydrogen is bonded to something other than itself, the numbers of hydrogens depends on the charge of the other atom.

Let’s take dioxygen for example:

Explaining by the common “Octect-reason” of classical Lewis Model.

Oxygen atom has 6 valence electrons(incomplete octet), so it tends to react with other atoms to fill its outermost shells. So it is unstable.

Oxygen molecule has become stable as both atoms in oxygen molecule achieve complete octet by sharing of electrons.