The modern periodic table

4th Quarter

THE MODERN PERIODIC TABLE

After a series of revisions, the early periodic table has evolved into what it is now. In the modern periodic table, the elements are arranged horizontally in order of increasing atomic numbers. Each element is identified by its symbols placed at the middle of the square; the atomic number and the atomic mass are also included.

THE GROUPS• also known as families• 18 vertical columns in the periodic table

• elements have similar chemical properties due to their similarities in the number of electrons in their outer shells

• composed of two categories:

a. Group A (Representative Elements)b. Group B (Transition Metals)

GROUP A (REPRESENTATIVE ELEMENTS)• Group IA – Alkali Metals (except Hydrogen)

• Group IIA – Alkaline Earth Metals

• Group IIIA – Aluminum Group/Boron Family

• Group IVA – Carbon Family

• Group VA – Nitrogen Family

• Group VIA – Oxygen Family/Chalcogens

• Group VIIA – Halogens

• Group VIIIA – Noble/Inert Gases

GROUP B (TRANSITION ELEMENTS)• found in between Group IIA and Group IIIA and

referred to as the d-block• inner transition elements (lanthanides and

actinides) are found at the bottom of the table and referred to as the f-block

THE PERIODS• also known as series• seven horizontal rows

• Period 1 – 2 elements; electrons occupy only 1 main energy level, s-sublevel

• Periods 2 and 3 – 8 elements; eight electrons in the s- and p-sublevels

• Periods 4 and 5 – 18 elements each; eighteen electrons in the s-, p- and d-sublevels

• Periods 6 – 32 elements; 32 electrons in the s-, p-, d- and f-sublevels.

- 14 elements from 58 – 71 were removed and placed at the bottom to form the Lanthanide series.

• Period 7 – 14 elements; placed at the bottom part of the table to form the Actinide series; incomplete period

• Inner Transition Elements – last two periods

• Lanthanide Series = Rare Earth Elements

• Actinide Series = Heavy Rare Earth Elements

FOUR MAIN REGIONS IN THE PERIODIC TABLE

• Elements belonging to the same group have similar last sublevel configuration (lsc). Thus using the electron configuration of the elements, the periodic table can be divided into 4 regions or blocks such as s-, p-, d- and f-blocks.

Block Assigned Groups block Group 1A to 2A

(Representative Elements)

p block Group 3A to 8A (Representative Elements)

d block Group 1B to 8B (Transition Metals)

f block Inner Transition Elements

POINTS TO BE CONSIDER IN DETERMINING THE ELECTRON CONFIGURATION AND/OR POSITION OF ELEMENTS IN THE PERIODIC TABLE.

1. The Number of electrons in the outermost energy level or the valence electrons resembles to the group number.

2. The highest main energy level occupied by the electrons of the atom corresponds to the period where the element is located in the periodic table.

CONFIGURATION OF VALENCE ELECTRONS OF REPRESENTATIVE ELEMENTS

• s- and p-sublevels

• n represents the number of the highest main energy level

• n is same as the period number in the periodic table

Group Number General Valence Electron Cnfiguration

1A ns12A ns23A ns2np14A ns2np25A ns2np36A ns2np47A ns2np58A ns2np6

Example:

1. Magnesium (Mg) belongs to Group 2A,

Period 3

Atomic # = 12

Electron Configuration = 1s22s22p63s2

2. Arsenic (As) belongs to Group 5A, Period 4

Atomic # = 33

Electron Configuration = 1s22s22p63s23p64s23d104p3

3. Chlorine (Cl) belongs to Group 7A, Period 3

Atomic # = 17

Electron Configuration = 1s22s22p63s23p5

LET’S TRY!• Sodium

• Calcium

• Oxygen

CONFIGURATION OF VALENCE ELECTRONS OF TRANSITION ELEMENTS

• s- and d-sublevels (Transition Elements)

• s-and f-sublevels (Inner Transition Elements)

• n represents the number of the highest main energy level

• n is same as the period number in the periodic table

• Example:

1. Iron (Fe) belongs to Group 8B, Period 4

Atomic # = 26

Electron Configuration = 1s22s22p63s23p64s23d6

2. Technetium (Tc) belongs to Group 7B, Period 5

Atomic # = 43

Electron Configuration = 1s22s22p63s23p64s23d104p65s24d5

3. Berkelium (Bk) belongs to Group 1B, Period 7

Atomic # = 97

Electron Configuration = 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p67s25f9

LET’S TRY!• Manganese

• Zirconium

• Gold

REACTIVITY OF ELEMENTS• Octet Rule – the basis in understanding the

properties of the elements

- states that, atoms or ions often react to obtain exactly eight electrons in their valence shell.

ALKALI METALS• Group 1A of the periodic table

• All are very reactive in the their elemental form.

• They are very soft, lustrous metals.

• They form compounds with the halogens similar to table salt, a compound formed by sodium and chlorine.

HALOGENS• Group 7A

• very reactive

• form compounds with alkali metals

• Sodium chloride is a very stable compound because both the sodium ion and chloride ion has eight valence electrons or a complete octet.

NOBLE GASES• Group 8A

• have complete octet, very stable

• unreactive gases

• physical and chemical properties can be predicted from their position in the periodic table.

CLASSIFICATION OF ELEMENTS

METALS• usually found on the left side and at the center

of the periodic table.

• three-fourths of the discovered elements

• have high thermal and electrical conductivity

• have mobile particles that can carry thermal or heat energy and electrical charges from one point of the material to another

• also have the ability to lose electrons

METALS• In a group, from top to bottom of the periodic

table, metallic character increases.

• bottom elements of the periodic table, the most metallic; top elements, least metallic

• Across the period from left to right, metallic character decreases.

• right elements, least metallic; left elements, most metallic

METALS• bottom to left corner of the periodic table are the

most reactive metals

• more metallic, more reactive

• Group 1A and 2A – very reactive metals

• Transition Metals – less reactive among the metals

• Coinage metals – unreactive transition metals at room temperature (gold, silver, platinum); they do not react with most of the substances they come into contact with.

NONMETALS• lie on the right side of the zigzag line

• 22 known nonmetals, 11 are gases

• do not conduct heat and electricity well

• have little luster and seldom reflect light

• usually brittle

• tend to gain electrons

METALLOIDS• found along the zigzag line between the metals

and non metals

• can behave as either as a metal or a nonmetal

SYNTHESIS:• Describe the arrangement of elements in the

Modern Periodic Table.

• What is the basis of the groupings of the elements?

• What are the points to be considered in determining the electron configuration and/or position of elements in the periodic table.

ASSIGNMENT:• Study, study, study!

• Quiz #2 on Thursday, January 28.

Topics:

- Modern Periodic Table

- Properties and uses of common elements