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

Practice Exercises

Page 2.6 – Ex 2.1

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, 3eO: 2e, 6eCl: 2e, 8e, 7e

PSC 4012: Chapter 2

Practice Exercises

Page 2.9 – Ex 2.2 Page 2.10 – Ex 2.3

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 2Atomic numbers

PSC 4012: Chapter 2

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

Practice Exercises

Page 2.22 – Activity 2.1

PSC 4012: Chapter 2

Groups (Families)

Group ILi:2e, 1eNa: 2e, 8e, 1eK: 2e, 8e, 8e, 1e

Group IIBe:2e, 2eMg: 2e, 8e, 2eCa: 2e, 8e, 8e, 2e

Group V

N:2e, 5eP: 2e, 8e, 5e

Group ILi:2e, 1e

Na: 2e, 8e, 1eK: 2e, 8e, 8e, 1e

Group IIBe:2e, 2e

Mg: 2e, 8e, 2eCa: 2e, 8e, 8e, 2e

Group V

N:2e, 5eP: 2e, 8e, 5e

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

PSC 4012: Chapter 2

Practice Exercises

Page 2.24 – Activity 2.2

PSC 4012: Chapter 2

Periods

Period IH: 1eHe:2e

Period IILi: 2e, 1eBe:2e, 2eN: 2e, 5e

Period IIINa:2e, 8e, 1eP: 2e, 8e, 5eCl: 2e, 8e, 7e

Period IH: 1eHe:2e

Period IILi: 2e, 1eBe:2e, 2eN: 2e, 5e

Period IIINa:2e, 8e, 1eP: 2e, 8e, 5e

Cl: 2e, 8e, 7e

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 2Group 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. Cl2 , F2 , etc.)

PSC 4012: Chapter 2Group 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 2Isotopes

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

Practice Exercises

Page 2.21 – Ex 2.12 & 2.13

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 4012: Chapter 2

Example:

Knowing that there is a 98.99% of C-12 in nature, a 1.11% of C-13, and traces of C-14, calculate the atomic mass of Carbon (C):

= (12 * 98.99/100) + (13 * 1.11/100) + 14 (0/100)= 11.8668 amu + 0.1443 amu = 12.0111 amu (amu: Atomic Mass Unit)

PSC 4012: Chapter 2

Need another example of calculations?!(Table 2.10, page 2.19, Nitrogen)

Knowing that there is a 99.64% of N-14 in nature, and a 0.37% of N-15, calculate the atomic mass of Nitrogen (N):

= (14 * 99.64/100) + (15 * 0.37/100) = 13.9496 amu + 0.0555 amu = 14.0051 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 metalsGroup IIA: Alkaline-Earth metalsGroup VIIA: HalogensGroup 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)I1 * (relative abundance) I1 + (mass number)I2 * (relative abundance) I2 + ... + (mass number)In * (relative abundance) In +

PSC 4012: Chapter 2

Practice Exercises

Page 2.20 – Ex 2.7 – 2.11 Page 2.36 – 2.39 Ex 2.18 – 2.26