Henry Moseley studied characteristic X-ray spectra of elements. The graph which represents his observation correctly is Given $$v=$$ frequency of $$\mathrm{X}$$-ray emitted Z = atomic number

If the radius of the first orbit of hydrogen atom is $${\alpha }_0$$, then de Broglie's wavelength of electron in $$3^{\text{rd }}$$ orbit is :

Which of the following elements have half-filled f-orbitals in their ground state? (Given : atomic number $\mathrm{Sm}=62;\mathrm{Eu}=63;\mathrm{Tb}=65;\mathrm{Gd}=64,\mathrm{Pm}=61$ ) A. $\mathrm{Sm}$ B. Eu C. $\mathrm{Tb}$ D. Gd E. $\mathrm{Pm}$ Choose the correct answer from the options given below :

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R) Assertion (A): The first ionization enthalpy of $3\mathrm{d}$ series elements is more than that of group 2 metals Reason (R): In 3d series of elements successive filling of d-orbitals takes place. In the light of the above statements, choose the correct answer from the options given below :

The correct increasing order of the ionic radii is

Bond dissociation energy of "E-H" bond of the "${\mathrm{H}}_2\mathrm{E}$ " hydrides of group 16 elements (given below), follows order. A. $\mathrm{O}$ B. $\mathrm{S}$ C. Se D. $\mathrm{Te}$ Choose the correct from the options given below:

Match List I with List II .tg {border-collapse:collapse;border-spacing:0;} .tg td{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px; overflow:hidden;padding:10px 5px;word-break:normal;} .tg th{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px; font-weight:normal;overflow:hidden;padding:10px 5px;word-break:normal;} .tg .tg-7btt{border-color:inherit;font-weight:bold;text-align:center;vertical-align:top} .tg .tg-0pky{border-color:inherit;text-align:left;vertical-align:top} List I (Atomic number) List II (Block of periodic table) A. 37 I. p-block B. 78 II. d-block C. 52 III. f-block D. 65 IV. s-block Choose the correct answer from the options given below :

Given below are two statements : Statement I : The decrease in first ionization enthalpy from B to Al is much larger than that from Al to Ga. Statement II : The d orbitals in Ga are completely filled. In the light of the above statements, choose the most appropriate answer from the options given below

Inert gases have positive electron gain enthalpy. Its correct order is :

Which of the following statements are not correct? A. The electron gain enthalpy of $$\mathrm{F}$$ is more negative than that of $$\mathrm{Cl}$$. B. Ionization enthalpy decreases in a group of periodic table. C. The electronegativity of an atom depends upon the atoms bonded to it. D. $${\mathrm{Al}}_2{\mathrm{O}}_3$$ and $$\mathrm{NO}$$ are examples of amphoteric oxides. Choose the most appropriate answer from the options given below :

For elements $$\mathrm{B},\mathrm{C},\mathrm{N},\mathrm{Li},\mathrm{Be},\mathrm{O}$$ and $$\mathrm{F}$$, the correct order of first ionization enthalpy is

Given below are two statements: one is labelled as Assertion $$\mathbf{A}$$ and the other is labelled as Reason $$\mathbf{R}$$ Assertion A : The energy required to form $${\mathrm{Mg}}^{2+}$$ from $$\mathrm{Mg}$$ is much higher than that required to produce $${\mathrm{Mg}}^{+}$$ Reason $$\mathbf{R}:{\mathrm{Mg}}^{2+}$$ is small ion and carry more charge than $${\mathrm{Mg}}^{+}$$ In the light of the above statements, choose the correct answer from the options given below.

The correct order of electronegativity for given elements is:

The difference between electron gain enthalpies will be maximum between :

Which one of the following elements will remain as liquid inside pure boiling water?

Group-13 elements react with $${\mathrm{O}}_2$$ in amorphous form to form oxides of type $${\mathrm{M}}_2{\mathrm{O}}_3(\mathrm{M}=$$ element). Which among the following is the most basic oxide?

The starting material for convenient preparation of deuterated hydrogen peroxide ($${\mathrm{D}}_2{\mathrm{O}}_2$$) in :

The normal rain water is slightly acidic and its $\mathrm{pH}$ value is $5.6$ because of which one of the following?

Given below are two statements : Statement I : ${\mathrm{H}}_2{\mathrm{O}}_2$ is used in the synthesis of Cephalosporin Statement II : ${\mathrm{H}}_2{\mathrm{O}}_2$ is used for the restoration of aerobic conditions to sewage wastes. In the light of the above statements, choose the most appropriate answer from the options given below :

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R Assertion A : Hydrogen is an environment friendly fuel. Reason R : Atomic number of hydrogen is 1 and it is a very light element. In the light of the above statements, choose the correct answer from the options given below :