PERIODIC TABLE OF ELEMENTS

PERIODIC TABLE OF ELEMENTS

In 1869, Mendelee a Russian scientist was the first to construct table. But he arranged the element in other of increasing on atomic mass. He pointed out that element with similar property kept re-occurring at regular interval or period.

                The mendelee periodic table had may gapes which he predicted that there were un-discovered element which will these gapes, he even predicts the possible property of that element. But with the discovery of the electronic structure, it became clear that element do not vary with their atomic mass but atomic number. They even found a new element e.g. scandium, gallium etc. which have the predicted property of mendelee.

Therefore, the modern periodic law states that element are arranged according to their atomic number.

However, the following are the terminology to understand when dealing with periodic table.

GROUP

 This can easily be known as the vertical column of element which comprise eight columns in periodic table ranges from 0-7.

Note: element in the same group must have the number of valency electron at their outermost shell.

However, the element hydrogen does not fit to belong to any group, but for convenience, it is placed in group one of because of its lone electron.

                In group 0, helium has two electrons while other have eight electrons each in which they are un=reactive element known as rare or noble gas because of their complete shell when configured.

                In between group 2 and 3, there are some sets of elements lying within called transition group of element.

PERIOD

                This can be best described as the horizontal row of element on the periodic table which are numbered from 1 – 7. However, element in the same period have the same number of electron shell or orbital. Example, element in period 2 have two electron shell (K L).

Note: the number of valency electron increased by one across the period provided they are in the same period from left to right.

PROPERTIES OF A PERIODIC TABLE

1.       Atomic and ionic size: Atomic size can be easily means atomic radius i.e. distance between nucleus to the electron revolving around the orbit or shell/. It can also be defined as one half the distance closest approach between the nucleus of atom in the element substances

2.       IONIC SIZE: These are also similar to that of atomic size but it will be measured by the distance between the center of one ion and the center of its nearest neighbor of opposite charge.

This property shows ionic radius decrease across the period while it increases down the groups as an increase in atomic number.

3.       MELTING AND BOILNG POINT: Discovery from periodic table shows that some element are metals, metalloids and non-metal. Hence, element in group 1. 2, 3, have strong metallic ability i.e. metallic bond that will held them together. Therefore, their melting and boiling are very high.

Note: Group 4 element shows high melting and boiling point because the element has simple covalent bond that interlink the atoms together to form giant three-dimensional crystalline lattice e.g. diamond.  

4.       Electrical and thermal conductivity: they decrease across the period and increase down the group

5.       IONIZATION ENERGY: they are energy requires to remove a valency electron from an atom of elements to form an ion. Thus, ionization energy increase across a period and decrease down the group.

6.       ELECTRON AFFINITY: These are the energy required to gain a valency electron from an atom of the element to form univalent negative electron. Thus electron affinity decreases across the period while it increased down the group.

7.       ELECTRON GRAVITY: it is the power of that atom in is molecule to attract electron. Thus it increases across the period and decrease down a group. The most electro negative elements are F, Cl, Br, I

BRIEF PROPERTIES OF FAMILIES OF ELEMENT.

GROUP 1 ELEMENT

                All element that belong to these group have similar behavior e.g. Na, K, L, are the similar one. They are known as ALKALI METALS.

FEAUTRES OF GROUP 1 ELEMENT

1.       They are univalent element since they have one valency electron at their outermost shell.

2.       They are family of electrovalent when they are ionized

3.       They are good reducing agent

4.       They are good conductor of electricity

5.       They are electropositive i.e. they donate electron

K⁺

Na⁺

6.       They react with cold water vigorously to liberate hydrogen and form alkalis

FEATURES OF GROUP 2 ELEMENT

1.       They are divalent element

2.       They form electrovalent

3.       They are reducing agent

4.       The most familiar ones are calcium and magnesium

5.       They are also referred to as ALKALINE EARTH METAL

FEATURES OF GROUP 3 ELEMENT

1.  They are trivalent

2.  Its reducing agent is nil.

3.  Their oxide is insoluble in water

4.  Aluminum as a member react with steam above 600 Celsius to liberate hydrogen

5.  Both oxide and hydroxide are amphoteric in nature

FEAUTRES OF GROUP 4 ELEMENT

1.       They are tetravalent element

2.       They are increased in metallic property down the group

3.       They have oxidation number of t2 and t4

4.       Carbon and silicon as a member form covalent compound with hydrogen e.g. CH4

5.       Carbon does not react with water in any form

FEATURES OF GROUP 5 ELEMENT

1.       They are non-metallic i.e. they cannot conduct electricity

2.       They have two oxidation number of t3 and t5 from several oxides which have parallel characteristics e.g.

N2O3 Nitrogen(III)oxide

P4O6 Phosphorus (III)oxide

N2O5 Nitrogen(V)oxide etc.

NOTE: They are all acidic and will combined with water to form acid.

FEATURES OF GROUP 6 ELEMENT

The most common element in this group are oxygen and they exhibit some characteristics both physically and chemically.

1.       They are electron acceptor

2.       Oxygen as a member is slightly soluble in water while Sulphur as a member is insoluble.

3.       Both oxygen and Sulphur react directly with hydrogen to yield water and hydrogen, sulphide respectively

FEATURES OF GROUP SEVEN ELEMENT

The element in this group are referred to as HALOGEN FAMILY.  They are most reactive non-metals. There features as follows

1.      They are all non-metals

2.      They are diatomic molecules

3.      They are coloured

4.      They ionize to form univalent negative ions

5.      Their electronegativity decreases down the group

6.      Their melting and boiling point increased progressively

FEATURES OF GROUP 0 ELEMENTS (SOME MAY REFERRED TO THIS AS GROUP 8)

This group are known as rare or noble gases.

1.      They have no bonding electron at their outer most shell

2.      They are radiative element

3.      Their melting and boiling point increase down the group

4.      Their ionization energy decreases down the group

5.      They consist about 1% of composition of air

TRANSITION ELEMENT

FEATURES

They are all elements found within group 2 and 3

1.      They are all metallic and possess all metallic properties

2.      They are coloured ionize

3.      They can form complex ion.

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