Class 10 Science 2022 Board Exam

The electrons in the atoms of two elements X and Y are distributed in three shells having $1$ and $7$ electrons respectively in their outermost shells.
(a) Write the group numbers of these elements in the Modern Periodic Table.
(b) Write the molecular formula of the compound formed when X and Y combine with each other.
(c) Which of the two is electropositive ?

List two advantages of adopting the atomic number of an element as the basis of classification of elements in the Modern Periodic Table.
(b) Write the electronic configurations of the elements X (atomic number $13$) and Y (atomic number $20$).

What is a Döbereiner triad ? Why can't the following three elements form such a triad ?
N ($14$); P ($31$); As ($75$)
(Atomic masses are given in parenthesis)

Two elements, A and B belong to the 3rd period of Modern Periodic Table. Element A belongs to Group 1 whereas Element B belongs to Group 16.
Compare the following characteristics of A and B, giving justification for each :
(a) Atomic size
(b) Metallic character

The atomic number of a non-metal 'X' is $8$.
(a) Write the period number and the group number of 'X'.
(b) Draw the electron dot structure of its molecule.

The atomic number of an element 'X' is $11$.
(i) Write the electronic configurations of X and find its valency.
(ii) Write the formula and nature of its oxide.

(a) State Newland Law of Octaves.
(b) With an example, explain Dobereiner's Triads.
(c) List one limitation each of both the attempts mentioned in 'a' & 'b'.

A part of modern periodic table is given below. On its basis, answer the following questions :
| Group No. → | 1 | 2 | 13 | 14 | 15 | 16 | 17 | 18 |
| Period ↓ |
| 2 | | | A | | | B | | |
| 3 | E | | D | | | F | C | |
(a) Write the molecular formula of the compound formed by the combination :
(i) A and F
(ii) E and B
(b) Which of the element is a
(i) Noble gas
(ii) Metalloid

Write the electronic configuration of element X, given by its symbol as under :
${}_{20}^{40}\mathrm{X}$
(ii) Determine its position in the modern periodic table.
(iii) What is the nature of its oxide ?
(iv) Name one other element of its group.

(a) Write the molecular formula of the following carbon compounds :
(i) Methane
(ii) Propane
(b) Carbon compounds have low melting and boiling points. Why ?