Atomic Structure, Valency and Mole Idea

Strengthen atom-level understanding to solve formula and composition questions.

Level

Exam-focused

Study Time

20 min

Exam Relevance

High

Atomic Structure, Valency and Mole Idea visual

Core concepts

Atom, electron, proton and neutron basics.
Atomic number and mass number.
Valency and combining capacity.
Intro-level mole relation and formula interpretation.

Fast-solving rules

Use valency cross method carefully.
Keep charges balanced in ionic compounds.
Check formula by total positive/negative balance.

Common mistakes

Confusing atomic number with atomic mass.
Writing wrong subscripts from valency values.

Chapter-end mini quiz

5 quick questions from the question bank.

Question 1

There are six electrons, six protons and six neutrons in an atom of an element. What is the atomic number of the element?

6121824

Question 2

What is the maximum number of electrons in the M-Shell?

681832

Question 3

The species that has the same number of electrons as $^{35}_{17}Cl$ is

$^{32}_{16}S$$^{34}_{16}S^{+}$$^{40}_{18}Ar^{+}$$^{35}_{16}S^{2-}$

Question 4

For an element with atomic number 35, which one of the following will be the correct number of electrons in its valence shell based on Bohr's model of an atom?

1357

Question 5

In which of the following pairs are the ions isoelectronic?

$Mg^{2+}$, $Ar$$Na^{+}$, $O^{2-}$$Al^{3+}$, $Cl^{-}$$K^{+}$, $Ne$

Source Base

NCERT atomic structure basics and valency
CBSE worksheet pattern on valency and mole concept

Back to Chemistry Chapters Previous: Hydrogen, Oxygen, Nitrogen, Carbon Dioxide and Air/Water Next: Applied Chemistry: Materials and Everyday Products