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Trends in the properties of elements from left to right and up to down in the modern periodic table.

Trends in the properties of elements from left to right and up and down vary. The change in the properties of elements occurs due to the valance electrons and atomic size. Elements are arranged in the Modern periodic table in the increasing order of their atomic numbers. In the modern periodic table, there are 18 vertical columns known as the group of elements and 7 horizontal rows known as periods. The scientists found that there is a relationship between the atomic numbers of elements with their properties and thus concluded to the fact that the properties of elements are the periodic functions of their atomic number. There is periodic changes in the properties of element when we go left to right in a periodic table.In this respect the valency, atomic size, metallic and non-metallic properties of element changes.

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The Trends in the Valency of Elements From Left to Right and Up to Down In the Periodic Table

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Valency:

The valency of elements does not change when we go downwards in a group because all elements has the same valence electrons in a group.If we are going to determine the group number of an element having atomic number 12. The outermost electrons in it are 2, so it’s group number is 2, but this technic of calculating group number is applicable for non-transitional metals only.If we have the atomic number of an element 17, the outermost electrons in it are 7 that shows that it’s group number is 10 + 7 = 17,in the case of a few of metals, metalloids, and non-metals, we have to add 10 on the outermost electrons for the calculating group number.The number of shells in electronic configuration shows the periodic number of element.

The way of finding a group and Periodic number of Elements when its Atomic number is given

As an example what are the group number and periodic number of following elements whose atomic number is given as follows.

(i) 15 (ii) 13 (iii) 27 (iv) 7

(i) 15- 2,8,5, the electronic configuration shows that it’s outermost electrons are 5 and it is non-metals, therefore group number of the element is =10 +5=15 and periodic number is 3

(ii) 13-2,8.3, the electronic configuration shows that it’s outermost electrons are 3, in this case the group number is 10 + 3 = 13 and periodic number is 3

(iii) 27 – 2,8,8, 8, 1,the electronic configuration shows that it’s outermost electron is 1, but it is a transitional element so its group number = number of electrons in fourth orbit+ number of electrons in fifth orbit = 8 +1= 9 and periodic number is 5

(iv) 7 -2,5. the electronic configuration shows that it’s outermost electrons are 5, it is a non-metals so its group number is = 10+5 = 15 and periodic number is 2.

The Trends in the Atomic Size of Elements From Left to Right and Up to Down In the Periodic Table

Atomic size:

The term atomic size refers to the radius of an atom. The atomic size may be visualised as a distance from the nucleus to the outermost orbit of an isolated atom.The atomic radius decreases in moving from left to right along a period. This is due to an increase in positive charge at the nucleus thereby increasing force of attraction between nucleus and orbitals that forces orbitals of electron to come closure to the nucleus.In a group the size of atoms increases because in moving downwards I’m a group e new shell is added.

The Trends in the Metallic and Non-metallic properties From Left to Right and Up to Down In the Periodic Table

Metallic and Non-metallic properties:

The metallic property of an element is the tendency of an atom of donating electrons,from left to right the positive charge of the nucleus increases, thus the force of attraction between nucleus and electrons increases thereby moving left to right the metallic property also called electropositivity decreases because electrons are more tightly bounded by the nucleus and thus it is more difficult to donate electrons. In moving downwards the metallic property of the element increases because the force of attraction between the nucleus and outermost orbital decreases and thus it becomes easy to donate electrons.

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