General Chemistry

1. Faculty of Allied Medical Sciences General Chemistry (MGGC-101)

2. Chemical bonds & chemical reactions Supervision: Prof.Dr.Shehata El-Sewedy Dr.Fatma Ahmed

3. Outcomes By the end of this lecture, the students will be able to 1-Understand the meaning of chemical bond 2-learn to type of chemical bond 3-To differentiate between solute, solvent and solution 4-Recognize the meaning of electrolyte 5-To know types of chemical reactions 6-To differentiate between acids and bases

4. Chemical bonds

5. CHEMICAL BONDS: THE OCTET RULE Why do atoms bond together? More stable (has less energy) Octet Rule Atoms form bonds to produce the electron configuration of a noble gas because the electronic configuration of noble gases is particularly ) stable) For most atoms of interest this means achieving a valence shell configuraonof 8 electrons corresponding to that of the nearest noble gas Atoms close to helium achieve a valence shell configuraon of 2 electrons Atoms can form either ionic or covalent bonds to satisfy the octet rule How to describe bonding? The ionic bond: formed by the transfer of one or more electrons from one atom to another to create ions The covalent bond: results when atoms share electrons Atoms without the electronic configuration of a noble gas generally react to produce such a configuration

6. 1) Ionic Bonds Results from transfer of electrons from one atom to another such as NaCl, NaBr and so on. Electronegativity measures the ability of an atom to attract electrons

8. Ionic Bonds: One Big Greedy Thief Dog!

9. Electronegativities of Some of Elements The electronegativity increases across a horizontal row of the periodic table from left to right The electronegativity decreases go down a vertical column

10. F>O>N>C fluorine is the most electronegative atom. Ionic substances, because of their strong internal electrostatic forces, are usually very high melting solids, often having melting points above 1000 °C

11. 2 )Covalent Bonds Results from sharing of electrons by two atoms such as H-H, Cl-Cl, H-Cl and so on. Polar covalent bond ( between two atoms different in electronegativity)

12. Covalent Bonds

13. Polar Covalent Bonds: Unevenly matched, but willing to share.

14. Chemical reactions

15. Reaction without electron transfer Reaction with electron transfer 1-Combination1-Oxidation (loss of electrons) 2-Substitution 2-Reduction (gain of electrons) 3-Addition 3-Redox reaction (oxidation-reduction) 4-Combustion

16. Solution Solvent Solute A solution is a homogenous mixture of 2 or more substances The solute is(are) the substance(s) present in the smaller amount(s) The solvent is the substance present in the larger amount H2O Soft drink (l) Sugar

17. nonelectrolyte weak electrolyte strong electrolyte An electrolyte is a substance that, when dissolved in water, results in a solution that can conduct electricity. A nonelectrolyte is a substance that, when dissolved, results in a solution that does not conduct electricity.

18. Acid–base reactions

19. Acids : Is the substance that produces H+ ions when it dissolved in • Water • strong acid; it is a strong electrolyte. • weak acid:itis a weak electrolyte. • Acids can be divided into two classes • Strong Acids : Completely dissociate into its ions eg: HCl, HBr, HNO3and H2SO4 • HCl (aq) → H+ (qa) + Cl- (aq) • 100% dissociation • Weak acids : is the one dissociate incompletely into its ions eg: CH3COOH. • CH3COOH ↔ H + (aq) + CH3COO- (aq) • 1% dissociation

20. Base : Is the substance that produces OH- ions when it dissolved in water • strong base; it is a strong electrolyte. • weak base:itis a weak electrolyte. • Bases: can be divided into two classes • Strong Bases : Completely dissociate into its ions eg: NaOH and KOH • NaOH (aq) → Na+ (qa) +OH- (aq) • 100% dissociation • Weak Base : is the one dissociate incompletely into its ions eg: ammonia. • NH3(aq) + H2O(l) ↔ NH4+ (aq) + OH- (aq) • 1% dissociation

21. Examples of the acid-base reactions: Reaction of Sodium hydroxide and Nitric acid & reaction of Potassium hydroxide and Sulfuric acid. The Brønsted - Lowry theory of acids and bases. A Brønsted – Lowry acid: is a species which donates a proton (H+ ion) to another species. A Brønsted – Lowry base: is a species which accepts a proton from another species. You must have a reaction in order to name a species as a Brønsted - Lowry acid (B-L acid) or base.

22. Example HCl(aq) + H2O (l) H3O+(aq) + Cl-(aq) HCl is the B-L acid, it donates the proton to the H2O which is the B-L base since it accepts the proton (H+ion) Example NH3(g) + H2O(l)NH4+(aq) + OH-(aq) H2O is the B-L acid, it donates the proton to the NH3 which is the B-L base since it accepts the proton (H+ion).

23. Quiz time

24. Mention Brønsted- Lowry theory of acids and bases for the fowlloing reaction NH3(g) + H2O (l)NH4+(aq) + OH-(aq) HCl(aq) + H2O (l) H3O+(aq) + Cl-(aq) What is type of base for NH3? NH3(aq) + H2O(l) ↔ NH4+ (aq) + OH- (aq) What is type of acid for HCl? HCl (aq) → H+ (qa) + Cl- (aq) Order according forelectronegativity ? N,C, F,O,

25. Mention types of reaction?

26. Student Question

27. Define and give example electrolyte solute Acids Base Mention types of reaction?

28. Mention Brønsted- Lowry theory of acids and bases for the fowlloing reaction NH3(g) + H2O(l)NH4+(aq) + OH-(aq) HCl(aq) + H2O (l) H3O+(aq) + Cl-(aq) What is type of base for NH3? NH3(aq) + H2O(l) ↔ NH4+ (aq) + OH- (aq) What is type of acid for HCl? HCl (aq) → H+ (qa) + Cl- (aq) Order according forelectronegativity ? N,C, F,O,

29. Assignments

30. 1-Raymond Chang. Chemistry. 10th ed. 2009 2-Zumdehl. International edition. 2009 Recommended textbooks: