Position of hydrogen in the periodic table - class-XI

Since Helium (He) is a noble gas and does not combines with hydrogen. Because bond formation is only favored when the final state of the two elements is more stable than their initial state. If a hydrogen atom bonded with a helium atom, neither of their 1s and 2s atomic orbital will be half/fully filled, which causes both atoms to be energetically unstable. Such compound will most likely break down immediately back to their respective atomic state.

• Metal hydrides are metals which have been bonded to hydrogen to form a new compound. Any hydrogen compound that is bonded to another metal element can effectively be called a metal hydride. Generally, the bond is covalent in nature, but some hydrides are formed from ionic bonds.
  
• Hence option A is a correct answer.

Rogue element in the periodic table is hydrogen, as its properties are similar with several groups. (alkali metals and halogens)

Hydrogen has ${ 1e }^{ - }$ in outermost shell, in order to achieve stability either ${ e }^{ - }$ to be removed or added. When added it acquires a stable configuration forming duplet.

$H$ is the lightest element on earth as there is only $1$ proton and ${ 1e }^{ - }$. All the other elements have more than 1 electrons and protons along with neutrons.

Hydrogen is having similarities with alkali metals and halogens any many properties and hydrogen exists In atomic form in high temperature but the reason not satisfy the assertion so assertion and reason are true.

Halogens are highly electronegative and form anions, whereas hydrogen can form both H+ and H- but is generally considered to have a different electropositive character than halogens.

As helium is inert gas so hydrogen does not make any product with $He$.

Hydrogen shows all other properties like alkali metals (form cation, combine with halogens, reducing nature) but nature of oxide is different than metals.

Because hydrogen has ${ 1e }^{ - }$ in its outermost shell which is ready to be donated like that a group $1A$ (alkali metals). Also hydrogen can accept an ${ e }^{ - }$ to from ${ H }^{ - }$ having ${ 2e }^{ - }$ in outer shell which is stable this resembles to $VIIA$ group (Halogen family), as they also require only one ${ e }^{ - }$ to fulfill their incomplete octet.

Hydrogen resembles alkali metals and halogens in all its properties. The electronic configuration of hydrogen, alkali metals and halogens are $1s^1,  ns^1$ and $ns^2, np^3$ respectively. All are short by one electron from noble gas configuration. Hence, all have similar chemical properties.

Alkali metals have one electron present in their outer shell in group I so after losing one electron they become stable ions similarly hydrogen has lone electron in its shell after losing it shares the same character as alkali metal group.

Hydrogen has atomic number 1. It has monatomic form is the most abundant chemical substance and it has single proton and zero neutrons. It exists in diatomic form.

Alkali metals are electro positive in  nature it readily lose its valence shell electron, and hydrogen resembles like alkali metals.

The electronic configuration of the hydrogen atom is $1s^{1}$. So, it can act as an electron acceptor to complete its' outer orbital as well as it can act as an electron donor to donate its' outermost electron to gain stability like metals.

Hydrogen is both electropositive as well as electronegative.
Like alkali metals, H has tendency to lose its one valency electron to form unipositive hydrogen ion $H^+$.
Hence, hydrogen is electropositive in nature.
Like halogens, hydrogen has tendency to gain one electron and form uninegative ion $H^-$.
Hence, hydrogen is electronegative in nature.

Metallic hydrogen is a phase of hydrogen when it behaves as electrical conductor. At the high pressure of gigapascals hydrogen might exist as a liquid metal. Liquid metallic hydrogen is thought to be present in large amount in gravitationally compressed interiors of Jupiter and Saturn.

Hydrogen has one electron in its s orbital and it can lose its electron like alkali metals which are highly electropositive in nature for their tendency to lose single electron from its outer shell. So hydrogen is similar to alkali metals.Positive hydride ions react with oxides and hydroxides to form water and with carbonates to form water and carbon dioxide.

The electronic configuration of hydrogen is ${ 1s }^{ 1 }$ as it has only one electron in its single orbital. So, it can gain one or lose one electron from its s orbital, thereby, showing $+1$ or $-1$ valency.

1.Resemblance of H with alkali metals-Both have one electron in its valency shell and form positive ion by losing electron.

In alkali metals hydrogen is the only non metal diatomic hydrogen gas.

Hydrogen is a chemical element with chemical symbol H and atomic no. 1 with atomic weight 1.00794 amu,hydrogen is the lightest element on the periodic table. Its monatomic form is the most abundant in nature.

• Hydrogen has 1 electron in its outermost shell due to which it combines with other hydrogen by covalent bons and exists as diatomic molecule.
  
• Its ionisation enthalpy is very high due to which it does not loose electron and hence, is unable to form cation and ionic compounds. (Ionisation enthalpy is the energy required for the removal of electron from the gaseous isolated atom in its ground state.)

Hydrogen is the lightest element on the periodic table. Hydrogen forms covalent compounds with non metals. In ionic compounds hydrogen can take the form of negative charge when it is known as hydride or a cation.

The options A and B are the correct answers.
Hydrogen differs from elements of $I-A$ group as:
(A) hydrogen can form ionic as well as covalent bond whereas elements of $I-A$ group can form only ionic bonds.
(B) All elements of $I-A$ group are metals. Hydrogen (with very high ionization energy does not possess metallic character).
(C) $H^+$ ion is stable in water.

Group, I A are alkali metals while hydrogen is considered a nonmetal and hydrogen are in gaseous form while alkali metals are all solids at room temperature like sodium, potassium, etc.

Hydrogen differs from elements of $VII-A$ group as:

The atomicity of hydrogen is two. It has one electron in its outermost shell and hence, the valency of hydrogen is also one. Electronic configuration does not match as the s orbital is half filled in hydrogen, which leads to s-s bonding, while p-p bonding exists in halogens, due to vacancy in p orbital.

Hydrogen has same electronic configuration as it has only one electrons in its outermost shell. The valency of hydrogen is one and it is a good reducing agent. All these properties are similar to alkali metals.

IV A group has half filled valence shell like carbon or silicon and it shares it with the hydrogen singly filled s orbital. They resemble have comparable I.P. and E.A.

At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, non-metallic, highly combustible diatomic gas. It is highly flammable and forms an explosive mixture with air.

In HCl, H has + 1 oxidation state so it resembles IA group property.

Hydrogen has one electron in its outermost shell and attains duplet configuration after one more electron and attains stability.

Hydrogen has electron configuration of $ 1s^{1}$.To become stable it can either accept to get helium configuration that is a stable configuration or it can even donate one electron. Hence it is very confusing where to place either in the metals group as it donates or in nonmetal group as it accepts an electron. Hence it occupies a unique position in the periodic table.

At room temperature, the ratio of ortho to para hydrogen is 3:1. As the temperature decreases toward the liquefaction point, the equilibrium shifts toward para hydrogen, reaching 1:1 at the liquefaction temperature.

The earths crust contains nearly 1% hydrogen by weight. In free state($H _2$), it occurs only in traces in the atmosphere. It is mainly found in the combined state and not the free state. Important sources are water, acids, organic matter etc.

Hydrogen has an electronic configuration of $1s^1$. So, it can accept one electron to complete its' outermost orbital which resembles to group $17$ of the periodic table. 

The reactivity of halogens towards hydrogen decreases down the group due to the decrease in electronegativity and increase in bond length. Thus, F2 > Cl2 > Br2 > I2.

Hydrogen has +1 oxidation state in compounds with more electronegative elements e.g. $HF$. It has -1 oxidation state in compounds with more electropositive elements like $NaH$. In the above compounds with $Na$ and $F$ show +1 and -1 oxidation state respectively.