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Both helium (He) and beryllium (Be) have...

Both helium (He) and beryllium (Be) have two valence electrons.Whereas he represent a noble gas element,Be does no. Assign reason.

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The element He (z=2) has two electrons present in the only shell i.e k hsell since this shell can have a maximum of two electrons only therfore , he is a noble gas e,lement .The elements Be (Z=4) has electronnic configuration as : 2,2 .Although the second shell has also two electrons but it is not complete .It can still acomodate six more electrons .Therefore the element beryllium does not reprsetn a noble gas element.
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Both helium (He) and magnesium (Mg) have two valence electrons. He represents a noble gas element, but Mg does not. Assign reason.

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Knowledge Check

  • All alkali metals have one valence electron, ns^(1) , outside the noble gas core except :

    A
    Na
    B
    Fr
    C
    Cs
    D
    None of these

  • Most of the monatomic ions of the representative elements are obtained by removing all the valence electrons from the atoms of metallic elements. Once these atoms have lost their valence electrons, they have stable noble gas or pseudo noble gas configurations. Which of these elements forms a cation having pseudo noble gas configuration?

    A
    `Mg`
    B
    `Ga`
    C
    `K`
    D
    `Al`

  • Assertion: Helium and beryllium have similar outer electronic configuration. Reason: Both are chemically inert.

    A
    Both A and B true and R is the correct explanation A
    B
    Both A and R are true but R is not a correct explanation of A
    C
    A is true but R is false
    D
    A is false but R is true

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    Na, Mg and Al are the elements having one, two and three valence electrons respectively. Which of these elements (i) has the largest atomic radius, (ii) is least reactive ? Justify your answer stating reason for each.

    F, Cl and Br are elements each having seven valence electrons. Which of these: (i) has the largest atomic radius (ii) is most reactive? Justify your answer stating reason for each.

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