Chemistry 100 Fall 1999 Dr. Upali Siriwardane CTH 311 Phone Office Hours: M,W,F, Tu,Th 8:00-10:00 a.m. Test 1 : Chapters 1, 2, September 27 Test 2: Chapters 3, 4, October 18 Test 3: Chapters 5, 6, November 10 Make-up, Comprehensive, November 15

Three Chemical Laws: Law of Conservation of Mass: Law of Constant Proportions: Law of Multiple Proportions:

Law of Conservation of Mass Total mass after a chemical reaction is same as before the reaction. Hydrogen (4g) + oxygen (32g) gives water 36g after the reaction.

Law of Constant Proportions A given chemical compound always contains exactly the same proportion of elements by weight.

Law of Multiple Proportions When two elements make a series of chemical compounds, the ratio of the masses of the second elements that combine with 1 gram of the first element can always be reduced to simple whole numbers. C O E.g. carbon monoxide 1g 1.33g carbon dioxide 1g 2.66g

What is an Atom? Very small particle. Smallest particles of elements and molecules There about 110 types of elements or Atoms. Different atoms have different physical properties and chemical reactivity

What are these ? a) atoms b) nucleus c) electrons d) protons e) neutrons f) isotope g) atomic number(Z)

Atomic symbols Every atom has a symbol. It is obtained using the first letter of the element name. If the first letter is used... letters are used. Eg. hydrogen-H, helium-He. Some elements (about 11) the names were not in English. E.g., Sodium-Na (natrium-latin), potassium-K(kalium-latin).

Isotope Atoms of an element with different masses All isotpoes of an element have same atomic number Isotpes of an element have different number of neutrons in the nucleus Isotopic symbol: atomic symbol showing atomic number (Z) and mass number (A) 13 C- carbon-13 and 12 C- carbon-12

What is a mass spectrometer? Mass spectrometer measures masses of different isotopes of an elements and their fractional or percentages abundance. (figure 7.7, page 238)

How do you calculate average Atomic Mass? M a x a + M b x b = AAM 100 M a = mass of isotope a M b = mass of isotope b a = percent abundance of a b = percent abundance of b AAM = Average atomic mass (Reported on the Periodic Table)

How do you calculate average Atomic Mass? M a x a + M b x b = AAM M a = mass of isotope a M b = mass of isotope b a = fractional abundance of a b = fractional abundance of b AAM = Average atomic mass (Reported on the Periodic Table)

Gallium in nature consists of two isotopes, gallium-69, with a mass of u and a fractional abundance of 0.601; and gallium- 71, with a mass of u and a fractional abundance of Calculate the weighted average atomic mass of gallium. 1) M a x a + M b x b = AAM M a x a(%) + M b x b(%) 2) = AAM 100

M a ( 69 Ga ) = u, a = percent abundance of 69 Ga = x 100 M b ( 71 Ga ) = u, b = percent abundance of 71 Ga = x 10 We can obtain an equation with one unknown, AAM. AAM (Ga) = x(0.601 x 100) x(0.339x100) 100 AAM (Ga) = AAM (Ga) = = AAM (Ga) = u (amu)

Periodic Table Periodic table is an arrangement of all known element according to their atomic number and chemical properties.

Vertical columns- groups,families Horizontal columns- periods Elements in a group have similar chemical properties group 1 - alkali metal: Li, Na, K Rb, Cs, Fr group 2- alkaline earth metals:Be, Mg, Ca, Sr, Ba, Ra group 17 - Halogens: Cl, Br, I, At group 18 - Noble gases: He, Ne, Ar, Kr, Xe, Rn

What are these? Transition Metals Actinides Lanthanides Ionic Charges Poly atomic ions and their charges

Naming Chemical Compounds Naming depend on the type of compound Name:Sodium chloride Formula:NaCl Carbon tetrachloride-CCl 4 Common names: Water-H 2 O Systematic Names: names given starting from element names and/or following a certain rules

Types of Compounds Ionic compounds: Metal+non-metal –a) Type I ionic compound –b) Type II ionic compound Covalent Compounds non-metal+non-metal

Covalent compounds Naming is similar to ionic compound but prefixes are added in front of the name of elements to indicate number of atoms in the molecule. Dinitrogen pentoxide- N 2 O 5

Ionic compounds: a) Type I ionic compound –Main group metal ionic compounds: have fixed charges E.g. Sodium Na + and Ca 2+ b) Type II ionic compound –Transition metal ionic compounds: –have ions with different charges E.g. Iron :Fe 2+ and Fe 3+

Type I - Ionic Compounds Type I ionic compound: Metal name written first then nonmetal name with the suffix-ide added to the end. Converting name to formula, requires the charge on ions.

Type II- Ionic Compounds Type II ionic compound: Metal name written first with the ionic charge in parenthesis and in roman numerals, then nonmetal name with the suffix-ide added to the end. Converting name to formula, requires the charge on ions. E.g. Chromium(III)chloride-CrCl 3

Naming Hydrates Hydrates are substances that include water into their formula. The water is not actually part of the chemical substance and this is reflected in the way the formula is written. Example: CuSO 4. 5 H 2 O

Naming Acids formula starts with H HCl HNO 3 H 2 SO 4 HClO 3 H 3 BO 3

HClO hypochlorous ClO¯ ”hypochlorite HClO 2 chlorous ClO 2 ¯ chlorite HClO 3 chloric ClO 3 ¯ chlorate HClO 4 perchloric ClO 4 ¯ perchlorate HNO 3 nitric NO 3 ¯ nitrate HNO 2 nitrous NO 2 ¯ nitrite

Naming bases formula ends with OH NaOH sodium hydroxide Ba(OH) 2 barium hydroxide KOH potassium hydroxide NH 4 OH Ca (OH) 2