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

3. Supervision: Prof.Dr.Shehata El-Sewedy Dr.Fatma Ahmed Atoms, molecules and ions

4. Outcomes By the end of this lecture, the students will be able to 1-Recognize the significant figures in measurements 2-To differentiate between International System of Units 3-To know Dalton’s atomic theory 4-Understand Atomic number, Mass number and Isotopes 5-Know the meaning of molecule and its types 6-learn to the meaning of ion and its types

5. 3. Significant figures in measurements In any measurement, there is always a degree on uncertainty Rules to determine the number of significant figures ►The numbers recorded in a measurement are called significant digits or significant numbers. 1. Digits other than a zero are always significant. 854 ► 3 sig figures and 3.6 ► 2 sig figures 2 - Zeros between non-zero digits  are Significant. ► 4 sig figures and 30.76 ► 4 sig figures 3- Zeros at the beginning of number  are not significant. 012 ► 2 sig.fig. and 0.012 ► 2 sig.fig 4 - Zeros at the end of number and after the decimal point  are Significant. 19.60 ► 4 sig figures 5 - Zeros at the end without decimal point  May or may not be significant. (Use exponential notation). Example: 500 could have 3 sig figures ► 5.00 X 10 2 or have 2 sig figures ► 5.0 X 10 2 or have 1sig figure ► 5 X 10 2

6. Example

7. Significant figures in calculations 1- In multiplication and division The result must have the same number of S.F. as the number having the least S. F. in the calculation. e.g.7.5023  2.00 = 15.0046 wrong 5 S.F. 3 S.F  15.0 (only 3 S.F. Correct 34.103  0.0310 = 10.57193 wrong  10.6 (only 3 S.F.) correct

8. 2- In addition and subtraction The result must have the same number of decimal digits as the number with the least decimal digits in calculation. e.g.25.23 + 21.3207 = 46.5507 2 d.d. 4 d.d  46.55 (only 2 decimals) 10.31 + 0.002438 = 10.307562  10.31 (only 2 decimals)

9. Rounding Look at the leftmost digit to be dropped, then 1 -If this digit is greater than 5, add 1 to the last digit to be retained. Thus, rounding 1.2161 to 3 significant figures gives 1.22. 2 -If digit is less than five, drop it, Thus, rounding 1.2141 to 3 significant figures gives 1.21. 3 -If this digit is 5 : 15.55 = 15.6odd 15.45 = 15.4even

10. Example: Perform the following calculations and round the answers to the correct number of significant figures: a. b. c. d. 37.76 + 3.907 + 226.4

11. Solution: The factor 5.8 has the fewest significant figures; therefore the answer should be reported to two significant figures. Round the answer to 3.6 The number with the least number of decimal places is 5.41. Therefore, round the answer to two decimal places, to 5.01 The answer is 0.37. Note how you have lost one significant figure in the subtraction. The answer is 268.1

12. Units of measurement Measurement always consists of two parts, a number and a unit. 1-Metric system

13. 2- International System of Units (SI system) This system is commonly used in all countries. Fundamental SI units

14. Some unit conversations: 1 kilogram = 1  10 3 gram 1 megagram = 1  10 6 gram 60 second = 60  10 15 femto second Femto second = 1  10 –15 second Pico meter = 1  10 –12 meter 1 meter = 1  10 12 pico meter Derived SI units Units which are not fundamental SI units called derived.  Area = (Length) 2  Volume = (Length) 3  Liter = 10 3 cm 3 = 10 3 mL  Velocity = m/s (length/time)  Density = g/cm 3 (mass/volume)

15. D ALTON ’ S A TOMIC T HEORY (1808) 1- Elements are composed of extremely small particles called atoms. 2-All atoms of a given element are identical, having the same size, mass and chemical properties. The atoms of one element are different from the atoms of all other elements. Atoms, molecules and ions

16. 3- Compounds are composed of atoms of more than one element. In any compound, the ratio of the numbers of atoms of any two of the elements present is either an integer or a simple fraction. 4- A chemical reaction involves only the separation, combination, or rearrangement of atoms

17. 8 X 2 Y 16 X8 Y +

18. S UBATOMIC P ARTICLES Particle Symbol Charge Mass Electron e - - 9.11X10 -28 g Proton p + + 1.67X10 -24 g Neutron n0 1.67X10 -24 g

19. An atom is neutral The net charge is zero Number of protons = Number of electrons Atomic number = Number of electrons Atomic number and Mass number Atomic number (Z) = number of protons in nucleus Mass number (A) = number of protons + number of neutrons = atomic number (Z) + number of neutrons X A Z Mass Number Atomic Number Element Symbol

20. 163165 O P Zn 81530 8 p + 15 p + 30 p + 8 n16 n35 n 8 e - 15 e - 30 e - S UBATOMIC P ARTICLES IN S OME A TOMS

21. Isotopes: The isotopes of an element have the same atomic no. (same chemical properties) but differ in their mass no. (different physical properties) i.e they have same no. of protons but different no. of neutrons. Example: the isotopes of hydrogen

22. Eg. 12 C, 13 C The 2 atoms have the same at.no. (equal no. of protons) But they differ in their mass no. (different no. of neutrons) 12 C: at.no.= 6,mass no.=12, no. of neutrons=6 13 C: at. no. =6, mass no.=13, no. of neutrons=7 Eg. O atom 16 O, 17 O, 18 O 8p, 8p, 8p 8n, 9n, 10n 8e, 8e, 8e

23. A molecule is an aggregate of two or more atoms held together by chemical forces H2H2 H2OH2ONH 3 CH 4 A diatomic molecule contains only two atoms H 2, N 2, O 2, Br 2, HCl, CO A polyatomic molecule contains more than two atoms O 3, H 2 O, NH 3, CH 4 Molecules and Ions The forces that hold atoms together in molecules are called chemical bonds.

24. Molecules can be represented in several different ways: Chemical formula Represent the type and actual number of atoms in a molecule, for example, carbon dioxide CO 2 (it has 1 carbon atom and 2 oxygen atoms). Structral formula Formula by which the individual bonds are shown (may or may not show the actual shape of molecule). Example

25. Ions An ion is an atom, or group of atoms, that has a net positive or negative charge. An ion may be a cation or an anion. Cation : ion with a positive charge. If a neutral atom loses one or more electrons it becomes a cation. Anion: ion with a negative charge. If a neutral atom gains one or more electrons it becomes an anion.

26. Quiz time

27. What is the number of protons and electrons in S 2 – What is the number of protons and electrons in aluminum ion, Al 3+ 16 O, 17 O, 18 O What is the number of protons, neutron and electrons in How many Significant figures and decimal points in

28. Student Question

29. What the SI units of 1-time 2-length 3-temperature 4-amount of substance 5-mass Answer the following operation 18.5+31.3= 3.2+5.09+3.007= 36.36÷4.04= 4.053÷4.00= 27.00x2.00= 0.0040x3001.37=

30. How many Significant figures in 1)32.01 2)5.010 3)32.00 4)200 5)8.1 Calculate the no. of proton, neutron and electrons for Define and give example: Cation Anion Isotope Structural formula

31. Assignments Group A and Group B Aya Salah- Omnia Gamal- Hanan Farg-Sarah Fasal Hashem Types of Ions Saad Mohamad El-sawi Mohamad Ahmad Fouad Mohamad Moawad El hussein Mohsen -Adel Ahmed Mahmoud Abd El- Mageed Uses of cations in industry Mana Allah Gamal- Malak Atef- Yasmine Abd ElHameed Applications of Isotopes Ali Hasan – Mahmoud Mohamad- Amir Mohamad- Mervat Abd El-Halim- Mervat Essam – Yasmine Rabee Applications of anions

32. R ECOMMENDED TEXTBOOKS : 1-Raymond Chang. Chemistry. 10th ed. 2009 2-Zumdehl. International edition. 2009