PSC 4012 Ionic Phenomena: A study of an environmental problem

PSC 4012: Chapter 2 Goals: _ SWBAT describe the current simplified atomic model _SWBAT describe the four most important families of the Periodic Table _SWBAT use and explain the relationship between electronic configuration and periodical properties

PSC 4012: Chapter 2 A model is a physical representation of something we cannot see (even without visible proofs we can demonstrate the existence of objects and explain their nature)

PSC 4012: Chapter 2 What have we learned about the evolution of the Atomic Model? Dalton’s (solid indivisible balls, no charge, different masses) Thomson’s (positive nucleus, embedded with negative electrons) Rutherford’s (atoms are mostly empty space, most mass is found at nucleus, light electrons surround it) Bohr’s (electrons revolve around nucleus in fixed levels or shells)

PSC 4012: Chapter 2 What is the simplified atomic model? How are the other models added to it?

PSC 4012: Chapter 2 Simplified Atomic Model  Mass of protons is similar to that of neutrons  Mass of electrons is negligible (1840 times smaller than mass of protons)  Number of protons: Atomic number  Number of protons and neutrons: Mass number

PSC 4012: Chapter 2

Simplified Notation  Fast way to inform about electronic configuration  Each level must be completed before moving to the next one  First level: 2e  Second level: 8e  Third level: 8e  Fourth level: 2e (for the purpose of this course)

PSC 4012: Chapter 2 Simplified Notation _Figure 2.3 (p. 2.8) B: 2e, 3e O: 2e, 6e Cl: 2e, 8e, 7e

PSC 4012: Chapter 2

Mendeleyev _Created first Periodic Table (page 2.15) _Organized elements according to Atomic Mass _Periodic: Columns of elements with similar properties _Predicted existence of elements according to observed periodicity (blank spaces in table)

PSC 4012: Chapter 2 Symbols:  You must know the name of the first 20 elements of the Periodic Table (plus a couple of very common metals)  Some elements are represented by a capital letter, others by a combination of two (capital and lower capital)  Examples: O (Oxygen), Fe (Iron)

PSC 4012: Chapter 2 Modern Periodical Table  90 natural elements  19 artificial elements  Elements are organized according to their atomic number  Horizontal rows represent Periods or Energy Levels  Vertical rows represent Groups or Families of elements, with similar chemical properties

PSC 4012: Chapter 2 Atomic numbers

PSC 4012: Chapter 2

Metals:  On the left of dark staircased-type line (except Hydrogen)  “Metallic” luster  Conduct electricity and heat  Solid at room T (except “Hg”, Mercury, liquid) Non-metals:  On the right of dark staircased-type line (also Hydrogen)  Do not have shiny luster  Do not conduct electricity or heat  Mostly gases at room temperature (except “Br”, Bromine, liquid)

PSC 4012: Chapter 2 Metalloids:  Along the staircase line (between metals and non metals)  Resemble non metals  Conduct electricity and heat

PSC 4012: Chapter 2

The number of the group (family) tells you the amount of electrons in the last shell

PSC 4012: Chapter 2

The number of the period tells you the amount of energy levels for electrons to surround the nucleus

PSC 4012: Chapter 2 Group IA  Alkali metals  One electron in outermost shell  Very soft to touch  Extremely reactive with water, oxygen and halogens

PSC 4012: Chapter 2 Group IIA  Alkaline-Earth metals  Two electrons in outermost shell  Less soft to touch  Less reactive with water

PSC 4012: Chapter 2 Transition Metals  Heavy metals between groups IIA and IIIA

PSC 4012: Chapter 2 Group VIIA  Halogens  They have seven electrons in their outermost shell  They are very reactive  Never to be found alone (if not attached to another element, attached to themselves in diatomic molecules, e.g. Cl 2, F 2, etc.)

PSC 4012: Chapter 2 Group VIIIA  Noble Gases  They have eight electrons in their outermost shell  They are very inert  Do not react with anybody, and are considered rare gases for they account for only 1% of gases in atmosphere

PSC 4012: Chapter 2 Hydrogen  One of a kind  Lightest and most abundant element  Non-metal (gaseous)

PSC 4012: Chapter 2 Isotopes Atoms that have the same number of protons (and electrons), therefore they have the same atomic number (atomic number = # protons) Atoms that have different number of neutrons, therefore they have different mass number (mass number = # neutrons + # protons)

PSC 4012: Chapter 2 Isotopes notation The higher the number of neutrons in an isotope, the lower its stability

PSC 4012: Chapter 2

The atomic mass of an element is the result of the mixture of its isotopes in different proportions The proportion of an isotope is expressed as a percentage, and it is called “relative abundance” (table on page 3.28) Therefore, in order to calculate the real atomic mass of any element, you have to multiply the mass number of each isotope by their relative abundance percentage, and add them together.

PSC 4010: Chapter 3 Example: Knowing that there is _98.99% of C-12, _a 1.11% of C-13, _and traces of C-14, in nature. Calculate the atomic mass of Carbon (C): AM (C) = (12 * 98.99/100) + (13 * 1.11/100) + 14 (0/100) AM (C) = amu amu AM (C) = amu (amu: Atomic Mass Unit)

PSC 4010: Chapter 3 Practice: Knowing that there is _99.64% of N-14, _and 0.37% of N-15, in nature. Calculate the atomic mass of Nitrogen (N): AM (N) = (14 * 99.64/100) + (15 * 0.37/100) AM (N) = amu amu AM (N) = amu

PSC 4012: Chapter 2 What have we learned so far? Modern Periodic Table organized in increasing number of atomic number (or # protons or # electrons) Each group’s number is equal to the number of electrons in outermost shell Each period’s number is equal to the number of energy levels (orbits) of electrons Metals are found on the left of dark stair cased-type line (except Hydrogen) Non-metals are found on the right of dark stair cased-type line (also Hydrogen) Group IA: Alkali metals Group IIA: Alkaline-Earth metals Group VIIA: Halogens Group VIIIA: Noble Gases

PSC 4012: Chapter 2 What have we learned about isotopes? Isotopes are atoms of the same element, with same atomic number, but different atomic mass (mass number) Same atomic number, therefore, same number of protons (and electrons) Mass number is the closest integer to which atomic mass (a decimal) is rounded up to Mass number = Atomic number (# protons) + # neutrons Atomic mass = (mass number)I 1 * (relative abundance) I 1 + (mass number)I 2 * (relative abundance) I (mass number)I n * (relative abundance) I n +

PSC 4012: Chapter 2 Practice Exercises  Page 2.20 – Ex 2.7 – 2.11  Page 2.36 – 2.39 Ex 2.18 – 2.26