   Question Answers

# What is meant by the term ‘coordination number’?  Hint: In complexes, there are ions, molecules or atoms which are bonded to the central metal atom. In crystals, each ion is surrounded by a specific number of ions of opposite charge.

Complete step by step solution:
- Coordination number is also known as ligancy. This term is mainly used in crystallography and materials science. Coordination number is the number of atoms, molecules or ions bonded to a central metal atom. The ions, molecules or atom surrounding the central metal atom is called ligands. This is in the case of complexes.
- In complexes formed by d-block transition metals, the most common coordination number is 6 and the structure is octahedral. Metals of f-block can have higher oxidation numbers because of their greater ionic radii and availability of more orbitals for bonding. They have a coordination number varying between 8 to 12.
- In case of crystals, the coordination number is the number of ions that is present in the immediate surroundings of an ion of opposite charge in a crystal lattice. For example, NaCl has a face centered cubic lattice. Each sodium ion is surrounded by six chloride ions and each chloride ion is surrounded by six sodium ions. So, the coordination number for NaCl is 6.
Thus, coordination number is the number of ions, atoms or molecules bonded to a central atom in coordination chemistry. In crystallography, it is the number of ions in immediate surroundings of an ion.

Note: The concept of coordination number in crystals and complexes is slightly different. In the former, it means the number of species bonded to a central metal atom and in the latter; it is the number of immediate negatively charged ions surrounding a positively charged ion and vice versa.
View Notes
Neural Control and Coordination  Derivation of Reynolds Number  Number System  Number Name 1 to 50  CBSE Class 9 Maths Chapter 1 - Number Systems Formulas  Number of Moles Formula  Octal Number System  What is the full form of phd?  Structure of Atom  How to Find Square Root of a Number  Important Questions for CBSE Class 12 Chemistry Chapter 9 - Coordination Compounds  NCERT Books Free Download for Class 12 Chemistry Chapter 9 - Coordination Compounds  Important Questions for CBSE Class 10 Science Chapter 7 - Control and Coordination  Important Questions for CBSE Class 12 Chemistry Chapter 1 - The Solid State  Important Questions for CBSE Class 12 Chemistry  Important Questions for CBSE Class 12 Chemistry Chapter 7 - The p-Block Elements  Important Questions for CBSE Class 12 Chemistry Chapter 5 - Surface Chemistry  Important Questions for CBSE Class 9 Maths Chapter 1 - Number Systems  Important Questions for CBSE Class 12 Chemistry Chapter 8 - The d and f Block Elements  Important Questions for CBSE Class 11 Chemistry Chapter 2 - Structure of Atom  Chemistry Question Paper for CBSE Class 12  CBSE Class 12 Chemistry Question Paper 2020  Chemistry Question Paper for CBSE Class 12 - 2013  Chemistry Question Paper for CBSE Class 12 - 2015  CBSE Class 12 Chemistry Question Paper 2017 - Free PDF  CBSE Class 12 Chemistry Question Paper 2019 - Free PDF  CBSE Class 12 Chemistry Question Paper 2018 - Free PDF  Previous Year Question Paper for CBSE Class 12 Chemistry - 2014  Chemistry Question Paper for CBSE Class 12 - 2016 Set 1 E  Chemistry Question Paper for CBSE Class 12 - 2016 Set 1 S  NCERT Solutions for Class 12 Chemistry Chapter 9  NCERT Solutions for Class 11 Biology Chapter 21  NCERT Solutions for Class 11 Biology Chapter 22  NCERT Solutions for Class 10 Science Chapter 7  NCERT Solutions for Class 12 Chemistry Chapter 9 Coordination Compounds in Hindi  Lakhmir Singh Chemistry Class 9 Solutions Chapter 4 - Structure Of The Atom  Surface Chemistry NCERT Solutions - Class 12 Chemistry  NCERT Solutions for Class 12 Chemistry Chapter 1 The Solid State in Hindi  RS Aggarwal Class 9 Solutions Chapter-1 Number Systems  NCERT Solutions for Class 11 Biology Chapter 22 Chemical Coordination and Integration in Hindi  