Chemistry · Chemical Bonding · NEET
It is the force of attraction that ties two atoms together so they stay close as one unit (a molecule). It is not a solid stick or a rope. It is an electrical attraction: the positive nucleus of one atom pulls on shared or transferred electrons. For NEET, remember a bond is always about electrons and the pull between charges.
Atoms combine to reach a LOWER energy state, because lower energy means more stable. Two separate atoms have higher energy. When they bond, energy is released, so the joined molecule sits lower and is harder to break apart. This 'drop to lower energy' is the single reason all bonds form. It matters for NEET because many questions test stability, not just structure.
Forming a bond RELEASES energy (it is exothermic). Breaking a bond ABSORBS energy. This is the opposite of what many students guess. So when H + H join to form H2, energy comes out. The amount of energy released when a bond forms equals the energy needed to break it later, called the bond dissociation enthalpy.
Stable means low energy and not eager to react. Noble gases (He, Ne, Ar) are stable because their outer shell is full. Other atoms try to copy this full-shell arrangement by sharing, gaining, or losing electrons. This drive to complete the outer shell (the octet rule) is why atoms bond. NEET links this directly to the octet rule and Lewis symbols.
No. A chemical bond is an electrostatic (electrical) force between charged particles: nuclei and electrons. It is far stronger than gravity between atoms. There are different bond types (ionic, covalent, metallic), but all come from the same idea: opposite charges attract and this lowers the total energy of the system.
More energy released when a bond forms means a stronger bond and a deeper energy 'valley'. A stronger bond is harder to break, so it has a higher bond dissociation enthalpy. NEET tests this with orders like Cl2 > Br2 > F2 > I2, where F2 is unusually weak because its small atoms crowd their lone pairs and push each other.
Which one of the following orders is correct for the bond dissociation enthalpy of halogen molecules?
Which of the following pairs of ions is isoelectronic and isostructural?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is the attractive force that holds atoms together in a molecule so they act as one stable unit.
To lower their energy and become more stable, usually by completing their outer electron shell like a noble gas.
Making a bond releases energy (exothermic). Breaking a bond needs energy (endothermic).
Ionic (electrons transferred), covalent (electrons shared), and metallic. Coordinate bonds are a special covalent type where one atom gives both electrons.
A full outer shell (octet, or duplet for H and He) has very low energy, so the atom does not need to gain, lose, or share more electrons.
