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💡 Give and take
Some atoms would rather give an electron away, others love to grab one. That hand-off creates charged ions that then cling together — an ionic bond.
How does a sodium cation form?
- Sodium (Z = 11) has 1 valence electron (2, 8, 1).
- It loses that electron to become stable.
- Now it has 11 protons and 10 electrons → a +1 charge → sodium cation Na⁺ .
How does a chloride anion form?
- Chlorine (Z = 17) has 7 valence electrons; it needs 1 more.
- It gains one electron to complete its octet.
- Now it carries a −1 charge → chloride anion Cl⁻ .
What is an ionic bond?
- Cations and anions are together called ions .
- Oppositely charged ions attract by an electrostatic force .
- This force of attraction holding them together is an ionic bond (e.g. in NaCl).
🧵 Threads of Curiosity
Ionic compounds do not stay as single units. They form 3-D crystals with ions in a repeating pattern — in NaCl each Na⁺ is surrounded by six Cl⁻, and each Cl⁻ by six Na⁺. This regular repeating pattern is the crystal structure , drawn as a crystal lattice .
NCERT Question 1 — A particular element (A) has
A particular element (A) has one electron in its third shell. There is another element (B) with six electrons in its second shell. (i) How many electrons does A tend to give or take to become stable? (ii) What kind of ion would it form? (iii) How many electrons does B tend to give or take to become stable? (iv) What kind of ion would it form? (v) If A and B were to combine, what kind of bond would be formed? (vi) What would be the formula for the compound thus formed?
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NCERT Question 7 — Which of the following, in
Which of the following, in Fig. 9.18, correctly represents Cl⁻ ion (Atomic number of chlorine = 17).
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NCERT Question 12 — If a species has 11
If a species has 11 protons, 12 neutrons and 10 electrons then (i) what is its atomic number and mass number? (ii) is it neutral, a cation or an anion? Explain. (iii) write its electronic configuration. (iv) name the species.
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NCERT Question 13 — Two elements, A and B,
Two elements, A and B, have the following configurations — A: 2, 8, 5 B: 2, 8, 7 (i) Which element is more reactive? (ii) Will A and B form ionic or covalent bonds when they combine? Explain using electron transfer or sharing. (iii) Predict the formula of the compound they would form.
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NCERT Question 15 — The species 27Al, 80Br– and
The species ²⁷Al, ⁸⁰Br⁻ and ²⁰¹Hg²⁺ have 13, 35 and 80 protons, respectively. How many electrons and neutrons do they have?
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Important Definitions
- Cation — a positively charged ion formed when an atom loses electrons, e.g. Na⁺.
- Anion — a negatively charged ion formed when an atom gains electrons, e.g. Cl⁻.
- Ionic bond — the electrostatic force of attraction between oppositely charged ions.
- Crystal lattice — the regular repeating three-dimensional arrangement of ions in an ionic solid.
