(a) What is an ion ? How is an ion formed ? Explain with the help of two examples of different ions.
(b) The valencies (or charges) of some of the ions are given below :

Ion Valency (Charge) Ion Valency (Charge)

Sodium ion 1+ Bromide ion 1–

Ammonium ion 1+ Hydroxide ion 1–

Calcium ion 2+ Sulphate ion 2–

Lead ion 2+ Phosphate ion 3–

Using this information, write down the formulae of the following compounds :
(i) Sodium phosphate
(ii) Ammonium sulphate
(iii) Calcium hydroxide
(iv) Lead bromide

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Solution

(a) An ion is an electrically-charged atom or molecule in which the total number of electrons is not equal to the total number of protons.
An ion is formed when a neutral atom loses or gains electrons. This loss or gain of electrons imparts a charge (positive or negative) to the neutral atom making it an ion.
There are two different types of ions:
If a neutral atom loses an electron, an overall positive charge is imparted to the atom and it becomes a positively-charged ion. A positively charged ion is called a cation. In a cation, the total number of electrons is less than the total number of protons as compared to the neutral atom. For example, sodium readily loses an electron to become a positively-charged sodium ion (Na⁺).
If a neutral atom gains an electron, an overall negative charge is imparted to the atom and it becomes a negatively-charged ion. A negatively-charged ion is called an anion. It has more no of electrons than the number of protons compared to the neutral atom. For example, chlorine readily gains an electron to become a negatively-charged chloride ion (Cl^-).

(b) Formula of the listed compounds are as follows:
Sodium phosphate – Na₃PO₄
Ammonium sulphate – (NH₄)₂SO₄
Calcium hydroxide – Ca(OH)₂
Lead bromide – PbBr₂

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Similar questions

Q. (a) What is the difference between a cation and an anion ? Explain with examples.
(b) The valencies (or charges) of some of the ions are given below :

Ion	Valency (Charge)	Ion	Valency (Charge)
Sodium ion	1+	Nitrate ion	1–
Copper ion	2+	Sulphide ion	2–

Using this information, write down the formulae of :
(i) Sodium sulphide
(ii) Copper nitrate

Question 111

An atom changes to a charged particle called ion, if it loses or gains electrons. The charge on an ion is the charge on electrons plus charge on protons. Now, write the missing information in the table given below :
$\begin{matrix} Name of ion & Proton charge & Electron charge & Ion charge (a) Hydroxide ion & + 9 & - & - 1 (b) Sodium ion & + 11 & - & + 1 (c) Aluminium ion & + 13 & - 10 & - (d) Oxide ion & + 8 & - 10 & - \end{matrix}$

Q. Using ammonium hydroxide, how would you distinguish between the following pairs of ions in solution:
(a) Ferrous ion and Ferric ion.
(b) Zinc ion and Lead ion.

The reaction given below is an example of:
$B a (O H)_{2} (s) + 2 C u C N S (s) \to B a (C N S)_{2} (a q) + 2 C u O H (s)$

Q. Consider the given statements and choose the correct option:

Statement 1: Polyatomic ions can have either positive or negative charge.

Statement 2: Ammonium ion and phosphonium ion are negatively charged ions.

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