Let \( ABC \) be a triangle. Consider four points \( p_1, p_2, p_3, p_4 \) on the side \( AB \), five points \( p_5, p_6, p_7, p_8, p_9 \) on the side \( BC \), and four points \( p_{10}, p_{11}, p_{12}, p_{13} \) on the side \( AC \). None of these points is a vertex of the triangle \( ABC \). Then the total number of pentagons that can be formed by taking all the vertices from the points \( p_1, p_2, \ldots, p_{13} \) is ___________.
Consider the following two reactions A and B: 
The numerical value of [molar mass of $x$ + molar mass of $y$] is ___.
Consider an A.P. $a_1,a_2,\ldots,a_n$; $a_1>0$. If $a_2-a_1=-\dfrac{3}{4}$, $a_n=\dfrac{1}{4}a_1$, and \[ \sum_{i=1}^{n} a_i=\frac{525}{2}, \] then $\sum_{i=1}^{17} a_i$ is equal to
The group 16 elements (oxygen group elements) of the periodic classification are also known as chalcogens because most of the copper ores have copper in the form of oxides and sulphides. The word chalcogen means “ore formation” which is derived from the Greek word “Chalcos” (Ore) and “gen” (formation).
There are 5 elements that come under Group 16 of the Modern Periodic Table namely:
The general electronic configuration of the chalcogens can be written as ‘ns2np4’, where ‘n’ denotes the value of the principal quantum number corresponding to the valence shell of the element.

The electron configuration of the synthetic element livermorium (believed to be a chalcogen) is predicted to be [Rn]5f146d107s27p4.