The chemical bonds

Biochemistry for nurses

The Chemical Bonds

مهني. حكيم دDr Hakim Mehenni

Email: dr.hakimmehenni.uqu@gmail.com

https://sites.google.com/site/drhakimmehenni/

Biochemistry for nurses

The Chemical Bonds • The chemical bond is a link between 2 atoms to give a molecule. • The chemical bond is composed by 2 electrons coming from the outer

layer of each different atom to make a pair of electron. • 4 types of chemical bonds: Nonpolar covalent bond, Polar covalent

bond, Ionic bond and Hydrogen bond.

nucleus

Outler electron

ATOM (hydrogen, oxygen, carbon…)

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Nonpolar covalent bond • Same forces of attraction onto the electron pair • The electron pair is situated at same distance

between the 2 atoms.• Often between same atoms (H2, O2, C4…)

Attractive forces (A = B)

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Polar covalent bond • Different forces of attraction onto the electron pair • The electron pair is situated closer to the more electronegative

atom than other.• Often between 2 different atoms (H2O, NH3, CH4…)

• Attractive force of B > attractive force of A

• Electronegativity of B > electronegativity of A

• Donor atom (δ+) = A

• Acceptor atom (δ-) = B

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Polar Molecules

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Ionic bond • An atom can win or lose electrons: Oxidation = the atom loses electrons

(ex: Na+); Reduction = the atom wins electrons (ex: Cl-). • The Oxidation and Reduction produce Ions. An ion is atom having a

missing electron (+) or an extra electron (-). An ion is electrically charged + or –

• An ionic bond is an interaction (attraction) between 2 ions having opposite signs.

Ionic compounds are salts!

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Hydrogen bond • A hydrogen bond is a attraction between polar molecules that occurs when a hydrogen (H) atom is bound to a highly electronegative atom (acceptor atom(δ-)). That hydrogen (donor δ+) is attracted towards some other nearby highly electronegative atom such as Oxygen (O), Nitrogen (N), Fluorine (F).

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• These Hydrogen bonds can occur between different molecules (intermolecular) such as water, or within different parts of the same molecule (intramolecular) such as DNA.

• The hydrogen bond is weaker than covalent and ionic

WATER

DNA

Biochemistry for nurses