ATOMIC STRUCTURE AND PERIODIC SYSTEM ELEMENTS

PERIODIC SYSTEM ELEMENTS

Development of the Periodic Table of Elements
Grouping elements by similar properties have evolved from the simple to the modern. The history of these developments are described in the following materials.

A. Development of Basic Grouping Elements

1. Grouping Elements Based on Metal and Non-Metal clusters are still too common as it turns out in a variety of metals and non-metallic elements are still there are many variations and the nature of the elements.

2. Law Triade Dobereiner In 1829, Johan Wolfgang Dobereiner see any resemblance between some elements of nature, and then breaks it down in terms of similar existing properties. Apparently each group consisting of three elements, the so-called Triade. If the elements are arranged according to the triade mass increases the atoms, it turns out the atomic mass and properties of the second element is the average of the atomic masses of the first and third elements.
These findings show an association between the atomic mass of the element properties. This grouping weakness lies in the fact that the number of elements with similar properties are not only 3 pieces.



3. Newlands Law of Octaves, 1864, A.R. Newlands announced the discovery of the so-called law of octaves. The elements are arranged by relative atomic mass increases. Apparently disputing elements 1 octave (element number 1 to 8, element number 2 to 9, and so on.) Shows similar properties or it could be said that the element properties change regularly. The trend is expressed as octaves Newland law, namely: If the elements arranged by atomic mass increases the properties of elements will be repeated after the eighth element.

Grouping Elements in Octave Newlands

t Newlands list compiled Octave, noble gas elements have not been
found. It turns out this is only suitable for grouping elements
light (low Ar).

4. law Mendeleyev
In 1869, the Russian scholar Dmitri Ivanovich Mendeleyev
based on observations of 63 elements known as
it concluded that the properties of elements periodic function of atomic mass
relative. That means if the elements are arranged according to the increase of mass
atom relative, certain properties will be repeated periodically.
Mendeleyev also made a list of periodic elements. The elements
which have similarities properties placed in a vertical column
called a class.
In classifying elements, Mendeleyev more emphasis
properties of the elements in the equation than the increase in mass of the atom
relative, so there are empty places in the periodic table
them. Empty places that will be filled later predicted
elements that have not been discovered at that time. At a later date the nature of prophecy
Similar corresponding predictions.
Weakness Mendeleyev Periodic Table as follows.
a. The placement of elements that do not correspond with the increase in mass of the atom
because it maintains relative similarity in the properties of elements
group.
b. There are many elements that have not been known at the time that the
there are plenty of empty tables.

Mendeleyev Periodic Table

5. Tabel Periodik Modern
Tahun 1914, Henry G. J. Moseley menemukan bahwa urutan unsur
dalam tabel periodik sesuai kenaikan nomor atom. Tabel periodik modern
yang disebut juga tabel periodik bentuk panjang, disusun menurut kenaikan
nomor atom dan kemiripan sifat. Tabel periodik modern ini dapat dikatakan
sebagai penyempurnaan Tabel Periodik Mendeleyev.
Tabel periodik bentuk panjang terdiri atas lajur vertikal (golongan) yang
disusun menurut kemiripan sifat dan lajur horizontal (periode) yang disusun
berdasarkan kenaikan nomor atomnya.
a. Lajur vertikal (golongan) ditulis dengan angka Romawi terdiri atas 18
golongan.
1) Golongan A (Golongan Utama)
Gol. IA : Alkali Gol.VA : Nitrogen
IIA : Alkali Tanah VIA : Kalkogen
IIIA : Aluminium VIIA : Halogen
IVA: Karbon VIIIA (0): Gas Mulia

PERIOD AND GROUPS IN MODERN SPU

1. Period

Is the horizontal rows of the periodic table.

Modern SPU consists of 7 periods. Each period stated amount / number of atomic shell elements that occupy those periods.

Period Number = Total Skin Atom

So:

The elements that have 1 skin (skin K only) located in period 1 (row 1), the elements of which have 2 skins (skins K and L) lies in the second period and so on.

example:

9F: 2, 7-second period

12mg: 2, 8, 2 the 3rd period

31Ga: 2, 8, 18, 3 period-4

Note:

a) Period 1, 2 and 3 is called the short period since it contains relatively few elements.

b) Period 4 and so called long period.

c) Period 7 called period is incomplete because not up to class VIII A.

d) To determine the period number of an element by atomic number, you only need to know the atomic number of the element that start each period.

2. Group

• periodic system consists of 18 vertical columns are divided into 8 main groups (group A) and 8 classes of transition (group B).

• The elements that have the same valence electrons are placed in the same group.

• For the elements of class A according to its place in the periodic system:

Group Number = Number of Valence Electrons

The elements of class A has another name, namely:

Group IA Alkali class =

Group IIA = class of Alkali Soil

Group IIIA = class of Boron

Group IVA class = Carbon

Group VA = class of Nitrogen

Group VIA = class of Oxygen

Group VIIA = class Halide / Halogen

Group VIIIA class = Noble Gases

PERIODIC PROPERTIES ELEMENTS

include:

1). Jari-Jari Atom

Is the distance from the nucleus to the electrons in the outer shell.

• The size of the atomic radius is influenced by the size of the atomic number of the element.

• The larger the atomic number of the elements of a class, the more the number of electron shell, so the larger the atomic radius.

So: in one group (from top to bottom), the atomic radius increases.

• In a period (from left to right), atomic number increases, which means the increasing nuclear charge, while the number of electrons fixed skin. As a result of the pull of the nucleus, the greater the outer electrons, resulting in increasingly smaller atomic radius.

So: in a period (from left to right), the atomic radius gets smaller.

2). Ionization Energy

Is the minimum energy required in the form of a gas of neutral atoms to release one electron to form charged ions +1.

If these atoms release electrons which the two then it would take more energy (called the second ionization energy), and so on.

EI 1 <EI 2 <EI 3 ff

In one group (from top to bottom), EI is getting smaller as the atomic radius increases, so gravity core to the outermost electron less. As a result, the outer electrons are easily released.

ü In a period (from left to right), EI greater because the atomic radius so small that gravity core to the outer electrons bigger / stronger. As a result, the outer electrons more difficult to remove.

3). Electron Affinity

• It is the energy released or absorbed by neutral atoms in gas form when receiving an electron to form negative ions.

• The price of a negative electron affinity, the easier atom receive / pull electrons and also the more reactive element.

• electron affinity is not the opposite of ionization energy.

• In one group (from top to bottom), the price of the smaller electron affinity.

• In a period (from left to right), the price of the greater electron affinity.

• main group elements have electron affinities are negative, except for groups IIA and VIIIA.

• has the largest electron affinity group VIIA.

4). electronegativity

• It is the ability of an element to attract electrons in a molecule of a compound (in bond).

• Measured using Pauling scale of between 0.7 (electronegativity Cs) to 4 (electronegativity F).

• Elements that have a large electronegativity prices, will tend to accept electrons and form negative ions.

• Elements that have small electronegativity prices, will tend to lose electrons and form positive ions.

• In one group (from top to bottom) rates, the smaller electronegativity.

• In a period (from left to right), the price of the greater electronegativity.