Chapter: The Periodic Table

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Table of Contents

Chapter: The Periodic Table Section 1: Introduction to the Periodic Table

Section 2: Representative Elements Section 3: Transition Elements

Table of Contents

Chapter: The Periodic Table Section 1: Introduction to the Periodic Table

What does periodic mean? • Periodic means with a repeating pattern • A periodic event is something that happens from time to time in a predictable way.

Periodic Table **Periodic Table is a table that shows all the chemical elements that have been discovered, arranged according to their properties, in a repeating pattern.

Mendeleev • Russian chemist that publish a version of a P.T. in which the elements were arranged according to their Atomic mass. • He observed that this arrangement revealed a pattern.

Importance of the periodic table and the importance of Mendeleev’s work: The importance of Mendeleev’s work lies on the periodic table repeating patterns that he observed and described. By analyzing the properties of different elements already present in the PT, he could infer the properties of elements that were not discovered yet. With time, these “missing” elements were discovered and located in the PT the empty spots.

The repeating patterns allow scientists to:

1) make predictions about an element’s chemical and physical properties, based on this element’s position on the periodic table. Elements with similar properties are placed in the same area of the periodic table. 2) Find the correct location for a new element, in the periodic table.

Atomic Mass X Atomic Number • Henry Moseley an English physicist realized that Mendeleev's table could be improved by arranging the elements according to atomic number ( number of protons in the nucleus of an atom) rather than atomic mass • That’ how the Periodic Table is organized today

Latest Version - the new elements/article

Atoms X Elements • Atoms are the building blocks of matter • Atoms form elements (one type of atom per element) ***Atoms have chemical and physical properties that will be kept by the elements

Textbook page 436

A period is a row of elements in the periodic table whose properties change gradually and predictably. Why???? Because the atomic number increases by one, when you move from one element to another. There are seven periods

• The groups are the columns. A group contains elements that have similar physical or chemical properties.

• The periodic table has 18 columns of elements and each one is called a group or family.

Each element has an element key

The Element Keys

• Name of the element, symbol, atomic number, atomic mass, the state of matter (at room temperature), if they are synthetic or not. • the color of the box will tell you the type of element ( metals, metalloids and non-metals)

Today’s Periodic table : Zones on the PT: textbook page 435 - read figure 2 • PT is divided in different zones: Representative Elements – Gr 1,2, 13 thought 18 Transition Elements – Gr 3 through 12 Inner Transition Elements – Two rows placed below

Metals – non metals and Metalloids in the PT – read page 438

Properties of Atoms and the pattern or trends in the periodic table • Atoms chemical and physical properties change according to the location of the atom in the periodic table • Some of the properties are: ionization energy, electronegativity, reactivity, atomic radius, melting and boiling point…

melting point and boiling point Usually metals have high melting and boiling points because the atoms are united by strong bonds.

Atomic radius –distance from the center of the nucleus to the last energy level of the electron cloud

Properties of Atoms: Atomic Radius

• The atomic radius is a term used to describe the size of the atom. • Atoms generally get smaller as you go across the periodic table and larger as you go down any one column.

Properties of Atoms: Atomic Radius

• The atomic radius is a term used to describe the size of the atom. • Atoms generally get smaller as you go across the periodic table and larger as you go down any one column.

Properties of Atoms: Atomic Radius • The electrons become tightly packed as you move across periods, so while there are more electrons for elements of increasing atomic number, the atomic radius actually may decrease

Properties of Atoms: Electronegativity • Is the tendency of an atom to attract the electrons of a bond when this atom is in a molecule. Ex: • The chlorine atom has a higher electronegativity than the hydrogen atom, so the bonding electrons will be closer to the Cl than to the H in the molecule.

From left to right: atoms in a period have more protons, so the + charge in the nucleus is stronger, attracting the electrons, that will tend to stay closer to the nucleus.

Properties of Atoms: Reactivity

• the capacity of an atom, to react with another atom or molecule. • Fluorine is the most reactive element • Helium is the least reactive element

Reactivity of Elements

Properties of Atoms: Ionization Energy • Ionization energy is the energy required to remove an electron from an atom in the gas state of matter, to form a positive ion • The higher the ionization energy, the more difficult it is to remove an electron, the atom is very stable.

Properties of Atoms: Ionization Energy • Ionization energy is the energy required to remove an electron from an atom in the gas state of matter, to form a positive ion • or • Is the energy required to remove an electron from an ion. • Helium is very stable, so it is very difficult to remove an electron from an atom of Helium.

• Sections 2 and 3

Transition Elements • The elements in Groups 3-12 are transition elements. They are all metals.

Common properties of Metals: • conduct electricity and heat, • solids at room temperature, except fpr mercury • shiny • low melting points • malleable and ductile ( can be turned into wires)

Transition Elements

• Reactive elements - usually found in nature combined with other elements – Less reactive than the metals in Groups 1 and 2.

Catalysts: Many transition elements are catalysts. A catalyst is a substance that can accelerate a chemical reaction but does not participate of this reaction. • EX: Nickel, zinc and cobalt • Many are synthetic.

Representative Elements Are found in groups 1 ,2, 13 and 18. They include metals, metalloids, and nonmetals.

Groups 1 and 2 • They’re called active metals because they react easily with other elements, forming new substances. • They are all metals except hydrogen, the first element in Group 1.

Common properties of Metals: • conduct electricity and heat, • solids at room temperature, except fpr mercury • shiny • low melting points • malleable and ductile ( can be turned into wires)

Representative Elements

Group 1 - Alkali Metals the most reactive of the metal groups, so these elements are always found, in nature, combined with other elements.

Hydrogen • Placed in Group 1 – because have only one electron in the last orbit, surrounding the nucleus, as all other elements in Group 1. • Could be also placed in Group 17( – it is a nonmetal ( gas) and need only one electron to became stable as all other elements in group 17.)

Representative Elements

Group 2 -Alkaline Earth Metals Alkaline earth metals are very reactive, but not as reactive as the alkali metals. Found in nature combined with other elements

Representative Elements

Group 17—The Halogen Group • Halogen means “salt-former.” • All of the halogens form salts with sodium and with the other alkali metals in Gr 1.

(GR 1 reacts easily w/ GR 17) Fluoride is the most reactive element in the periodic table

Representative Elements

Group 18—The Noble Gases • The Group18 elements are called the noble gases. • they rarely combine with other elements and are found only as uncombined elements in nature. • Their reactivity is very low.

Other Groups of Representative Elements Group 13 – Boron Group - has Aluminum Group 14 - Carbon Group Group 15 – Nitrogen Group – has also Phosphorus Group 16 – Oxygen Group – has also Sulfur

* Carbon, Nitrogen, Hydrogen, Oxygen, Sulfur are found in organic compounds such as proteins, nucleic acids, lipids and carbohydrates.