No. of moles of 34 g of NH₃ = 34/17 = 2

No. of molecules = 2 x 6.023 x 10²³

No. of atoms in one molecule of NH₃ = 4

No. of atoms in 2 molecules of NH₃

= 4 x 2 x 6.023 x 10²³ = 48.18 x 10²³

Magnetic quantum no. represents the orientation of atomic orbitals in an atom. For example p_x, p_y & p_z have orientation along X-axis, Y-axis & Z-axis

Δp = mΔv Substituting the given values of Δx and m, we get 1×10^–18 gcms^–1 = 9×10^–28g × Δv

The correct answer is Potassium.

Key Points

• Potassium belongs to a group - (1) and period - (IV) of the periodic table. Hence among the given options, Potassium has a maximum atomic radius.
• Carbon and Nitrogen belong to the period - (II) of the periodic table and on the right side hence it is obvious that atomic radii of Carbon and Nitrogen are very much small than Sodium and Potassium.
• Sodium and Potassium belong to a group - (1) and  Potassium is placed below Sodium hence the atomic radius of Potassium more than Sodium.

The correct answer is C-12.

The International Union of Chemists selected the most stable carbon isotope (C-12) or ¹²C as the standard for comparison of the atomic masses of various elements.

The mass of C-12 is taken as a 12 atomic mass unit (standard).

A Carbon-12 contains six protons, six neutrons, and six electrons.

The Law of Octaves was only valid up to the element calcium, because beyond calcium, every eighth element did not have properties that are identical to those of the first element.

Eka-aluminium and gallium are the same elements because the properties of Eka-Aluminium are almost identical to the qualities of the gallium element. Eka-Aluminium is a chemical element that has nearly identical properties to the gallium element. The properties of the elements, such as their atomic mass, density, melting temperature, the formula of chloride, and the formula of oxide, are nearly identical to those anticipated by Mendeleev in his theory.

The elements are listed in ascending order of atomic numbers, with heavier elements at the top of the list. The horizontal rows of the periodic table are referred to as Periods, and the vertical columns of the periodic table are referred to as Groups. The elements in the Modern Periodic Table are divided into seven Periods and eighteen Groups, as shown in the diagram below. The chemical elements are arranged from left to right and top to bottom in order of increasing atomic number, or the number of protons in an atom’s nucleus, which generally corresponds to increasing atomic mass. The elements are arranged from left to right and top to bottom in order of increasing atomic mass.