RSPT 1060MODULE B: Basic Chemistry

Lesson # 2

The Periodic Table

Web Sites:– http://www.chem4kids.com/

– http://staff.jccc.net/pdecell/chemistry/chemtext.html

– http://library.thinkquest.org/3659/

– http://www.webelements.com/webelements/scholar/

Objectives• At the end of this module, the student will be able to…

– Define terms associated with the period table and electron transfer.

– Identify the chemical symbol of the following elements commonly used in respiratory care (H, Li, Be, Na, Mg, Fe, K, Ca, Cu, Ag, Au, Zn,C, N, O, F, He, Ne, Si, P, S, Cl, Ar, Kr, Xe, Rn, Hg).

– Identify the macronutrients and micronutrients found in the human body.

– Describe the methods used to put elements in order on the periodic table.

– Explain the periodic law.– Differentiate between the two classification-

schemes commonly used in describing elements.– Describe the method of classification called

“Groups of Elements”.

Objectives• At the end of this module, the student should be able to…

– Identify the noble or inert gases, representative elements, transition metals and inner transition metals

– Describe the classification scheme called “Classes of Elements”.

– Using the periodic chart is able to identify an element as a metal, metalloid or non - metal.

– Describe the significance of the “Rows” or Periods.– Describe the significance of the “Columns” also

known as groups or families.– State the purpose of valence electrons.– Differentiate between a neutral and a stable atom– Explain the significance of location on the periodic

tale and the movement of electrons.– Describe the relationship of molecules and

compounds.

MAJOR TOPICS

1. A Look At The Elements

2. Organization of the Table

3. Valence Electrons & Bonding

Pure Substances

• Element – Large collection of atoms of the same type.– All have same atomic number.– Substance cannot be broken down further than

its individual atom, and still maintain its identity.

• Atom – smallest “particle” of an element. – Protons– Neutrons– Electrons

A Look At The Elements

117 Elements

Atomic Number

Element Name

Symbol or Abbrev.

Atomic Mass Unit (AMU)

1

Hydrogen

H

1.01

Organization of the Table

A. Order (Atomic Number)

B. Classification Schemes

C. Rows (or Periods)

D. Columns (groups or families)

Order

• Atomic Number from low to high. – Left to Right

– Based on the number of protons

Periodic Law• The periodic law states that when elements are

arranged in order of increasing atomic numbers, elements with similar properties occur at periodic (regularly reoccurring) intervals.

• There is a method to the madness!

• Arrangements– Rows– Columns

Classification Schemes

• GROUPS OF ELEMENTS - based on “Chemical Properties”– What determines the chemical properties?

• CLASSES OF ELEMENTS - based on “Physical Properties” – What determines the physical properties?

But First a Word About Electrons…

Electrons• Electrons are small, light, negatively charged

particles.• They surround (circle) the nucleus in a “cloud”

and are constantly moving.• The electrons stay in a particular orbit called a

shell (aka orbital or energy level).• Shells are groupings of atoms around the

nucleus like skin on an onion. – Electrons are not perfectly free to move about an

atom. – An electrons is restricted to moving only in a certain

region of space (shell), depending on the amount of energy it has.

Electron Configurations• The specific arrangement of electrons in an

atom’s shells is called the configuration.• There are up to seven shells into which

electrons can fit.• The order by which they load is fixed and

allows for the periodicity of the table.• The total amount of electrons possible in an

element is dictated by the capacity of the shell and can be determined by 2n2

,where n is the number of shells present.

• The movement of electrons between shells involves energy.

Shells or Energy Levels• The more shells, the farther the shells

are from the nucleus and the larger the atom.

• The more shells, the more electrons it can hold, and the more energy it has.

• Valence Electrons are electrons in the outer level and have the highest energy and are the most reactive of the electrons in the atom

Filling of shells• All shells contain subshells

– Electrons travel in subshells in pairs– Subshells are labeled “s”, “p”, “d”, “f”, “g”, “h”, “i”– Subshells do not fill from inside out, they have an

unusual but orderly method for filling. • First shell has 1 subshell (1s)• Second shell has 2 subshells (2s, 2p)• Third shell has 3 subshells (3s, 3p, 3d)• Fourth shell has 4 subshells (4s, 4p, 4d, 4f) • Special notation: 1s2, 2s2, 2p3 for nitrogen

• Electron shells correspond to the ROWS of the periodic table.– All elements in a given row have the same number

of electron shells.• First row, 1 shell• Second row, 2 levels of shells

Electron Representations• Two methods for representing the

electron configurations– Electron Configurations

• List all shells, subshells and electrons• Example: Mg 1s2, 2s2, 2p6, 3s2

– Lewis Dot Structures• Show only valence (outer shell) electrons• Example:

Mg:

Electron Dot Structures or Lewis Diagrams• Method of showing the number of

“valence” electrons (number in the outside shell)

H . He:Be: .N:

:S:s subshell

(1 pair)p subshell

(2 pair)

Sulfur has 16 electrons. 2 in first shell, 8 in second shell, 6 in third shell.

HOLD THAT THOUGHT…

GROUPSGROUPS Of Elements• More modern method of classification of

elements based on electron configurations and based mainly on “Chemical Properties”

– Representative or Main-group Elements (includes Noble Gases)

– Transition– Inner transition (Lanthanide series and Actinide

series)

Groups or Families • Vertical Columns 1 - 8

• Roman numerals or numbers & letters

• Elements in the same column have similar chemical properties.

• They often substitute for each other in chemical reactions.

• The roman numeral is the number of electrons in the outer shell.

Classes Of Elements• Early method of classification of

elements based mainly on “Physical Properties” .

– Metals– Non-metals– Metalloids (semi-metals)

Main-groups or Representative• Of greatest interest in medicine.

• Two groups on left and six on the right

3A1A

2A

4A

5A

6A

7A

8A

Main-groups or Representative

1A through 8A– Group 1A - Alkali metals are shiny, soft, low

melting metals. They react rapidly with water to form products that are highly alkaline and are never found in the pure state in nature.

– Group 2A - Alkaline earth metals are also lustrous, silvery metals, but are less reactive than 1A. Never found in pure state in nature

– Group 7A - Halogens are found in nature combined with other elements. (NaCl salt)

– Group 8A or 0- Noble gases are colorless gases of very low chemical reactivity. Some don’t even combine with anything.

Transition metal groups• Ten smaller groups in the middle

– 21 through 30– 39 through 48– 57 through 80– 89 thorough 112

• 1B through 8B

• Some not named yet (110-112)

Inner Transition Groups• Group of Fourteen elements in two rows usually

depicted at the bottom of a periodic table.• Subdivided into two “series”

– Lanthanide series– Actinide series

• Unique because– They can contain MORE than 8 electrons in its

outermost shell• Argon – 2-8-8• Scandium – 2-8-9-2

– Most elements can only use their outermost shell to “do business”. These elements can use their TWO outermost shells.

Summary on Groups• Based on chemical properties

– Electron configurations

• Three “groups”– Main

• 1A through 8A• Includes Noble gases

– Transition– Inner Transition

ClassesClasses Of Elements • Based on “Physical Properties”

• Metals

• Non-metals

• Metalloids (semi-metals)

Classes Of Elements

Alkali Metals• PHYSICAL PROPERTIES

– Left side of table– All solid at room temperature

except mercury– Usually hard– Usually high melting point– High density– Shiny, lustrous– Reflects light– Malleable– Conduct electricity and heat– Ductile (wire)

• CHEMICAL PROPERTIES – Does not readily combine with

other metals– Prefers to combine with non-

metals– May be found in free state

(simply as an element (gold, silver, copper, platinum)

Non-metals• PHYSICAL

PROPERTIES – Right side of table– Solid (5), liquid (1) or

gas (11) at room temperature

– Solid metals are brittle– Not malleable– Poor conductors of

electricity and heat (except carbon)

– Low density– Not silvery– Dull, poor light reflection– Low melting point

• CHEMICAL PROPERTIES– Combine with metals– Combine with other non-

metals– Few found in free state

(oxygen, nitrogen, carbon)

– Noble gases usually in free state and non-reactive with any other elements

Metalloids (semi-metals) • PHYSICAL

PROPERTIES– Located between metal

& non-metal on periodic table

– Along zigzag line– Solid at room

temperature– Exhibit properties of

metals & non-metals– Most are silvery– Brittle– Poor conductors (like

silicon, may be a semi-conductor)

– Increase temperature leads to increased conduction

• CHEMICAL PROPERTIES – Exhibit properties of

both metal & non-metal

Element Classification• Representative (Main) Elements:

– Have at lease one electron in the s or p subshell and desire to fill (or empty) those subshells.

• Transition elements: – Have at least one electron in the d subshell and

desire to fill that subshell.

• Inner transition elements: – Have at least one electron in the f subshell and

desire to fill that subshell

Valence Electrons & Bonding

• The outermost shell is most important for determining chemical properties.

• The outer shell contains the valence electrons.

• Valence electrons – These are the electrons that are lost, gained and shared when an atom unites (BONDS) or is involved in a chemical reaction.

Chemical Reaction• A chemical reaction takes place when

valence electrons are lost, gained or shared by other atoms to form a molecule.– Diatomic element (O2) – 2 of same atom

– Compound (H2O) - 2 or more different atoms

Oxygen

• Molecule of a Diatomic Element: Similar atoms sharing 2 electrons

– Oxygen + Oxygen = O2

• Molecule of a Compound: Different atoms sharing 1 electron

– Oxygen + Hydrogen = H2O

O O

O HH

Classes Of Elements • Metals

– electron donors – 1 to 3 valence electrons in outer shell – Usually end up as (+) ions or cations

• Non-metals – electron acceptors – 6 - 7 valence electrons in outer shell – Usually end up as (-) ions or anions – except for noble gases which have 2 or 8 and are

inert OR they don’t donate or accept

• Metalloids (semi-metals) – may donate or accept electrons – 4 - 5 valence electrons in outer shell usually (- or +)

Neutrality vs. Stability• Neutrality – all elements are neutral in their

pure state because the number of electrons (-) is equal to the number of protons (+).

• Stability – Except for the noble gases, all elements are unstable. Their outside shells are not full and they are looking for electrons.– The elements we typically deal with in medicine are

usually looking to fill their outer shell (s & p subshells) with 8 electrons.

Example• Oxygen needs 8 electrons in outer shell to be

“stable”• Rows indicate the number of shells. (2)• Atomic number indicates total number of electrons (8)• Columns indicate number of electrons in the outer shell.

(6)• Atoms what to fill their outer shell.

– Oxygen is looking for 2 electrons to become “stable” because it only has 6 valence electrons and needs eight in outer shell.

• 2 electrons to fill shell #1 (1s2)• 6 electrons to fill shell #2 (2s2, 2p4)

:O:

What can Oxygen do to become “stable”?• Molecule of a Diatomic Element:

Similar atoms sharing 2 electrons

– Oxygen + Oxygen = O2

• Molecule of a Compound: Different atoms sharing 1 electron

– Oxygen + Hydrogen = H2O