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đź’ˇ The urge to be stable
Atoms are like people chasing a full set — a complete octet. To get there they either share electrons or hand them over. That is the whole secret of chemical bonding.
What is a molecule?
Molecule
A neutral group of two or more atoms that can exist independently and shows the properties of the substance.
- An electrically neutral group of two or more atoms.
- It is capable of independent existence and shows all the properties of the substance.
- Elements can exist as molecules (e.g. Hâ‚‚); some, like helium, exist only as single atoms.
What is a chemical bond?
Chemical Bond
The force that holds atoms together when they combine and lower their energy to become stable. Formed by sharing or transferring electrons
- Atoms combine so the total energy of the system becomes lower (more stable).
- The force that holds atoms together is a chemical bond .
- Two main ways: sharing electrons (covalent) or transferring electrons (ionic).
Two Ways Atoms Combine
Sharing of electrons
Transfer of electrons
Atoms share a few or all valence electrons
One atom gives electrons, another accepts them
Forms a
covalent bond
Forms an
ionic bond
Example: Hâ‚‚, Oâ‚‚, HCl, Hâ‚‚O
Example: NaCl, MgClâ‚‚
NCERT Question 4 — Choose the correct statement(s) and
Choose the correct statement(s) and correct the false statement(s). (i) Elements are made up of molecules and compounds are made up of atoms. (ii) The molecule of a compound is always made up of two or more atoms of the same kind. (iii) One molecule of nitrogen gas contains three nitrogen atoms. (iv) Water is made of two hydrogen atoms, covalently bonded with one oxygen atom.
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Important Definitions
- Molecule — a neutral group of two or more atoms able to exist independently.
- Chemical bond — the force that holds atoms together after they combine.
How do atoms combine?
Atoms combine
By sharing or transfer
1. Covalent bond
Atoms share electrons
Example:
Water, methane
2. Ionic bond
Electrons transferred
Example:
Sodium chloride
