Charged Groups
Understanding radicals and ions
What this lesson covers
Why it matters
Imagine a group of atoms holding hands so tightly that they never let go, even when the molecule breaks apart.
Predict first
When sodium chloride dissolves, what happens to the sodium and chloride ions?
Ionic compounds dissociate into charged ions. These ions are the 'radicals' or charged groups that act as single units in reactions.
- They remain neutral atoms floating freely
- They split into charged ions that act as single units — correct
- They break down into protons and electrons
What you do
Build a neutral sodium atom — 11 protons, 12 neutrons and 11 electrons (mass number 23). Take one electron away and it becomes the Na⁺ ion: the same atom, now carrying a charge.
Check yourself
Which of the following is a charged group (radical) that acts as a single unit?
NO₃⁻ is a polyatomic ion (radical) with a net charge that stays together as one unit during reactions.
Why do we call ions 'radicals' in this context?
In ICSE Class 7 chemistry, 'radical' refers to an atom or group of atoms that carries a charge and behaves as a single unit.
- Oxygen atom (O)
- Nitrate ion (NO₃⁻) — correct
- Hydrogen gas (H₂)
- Because they are unstable and explode
- Because they act as a single unit with a specific charge — correct
- Because they have no electrons