While studying chemistry, you’ll come across a topic named periodic table. Each period table has 18 vertical columns called groups and seven horizontal rows called periods. As we move top to bottom down the group and left to right across a period, it shows different trends and patterns. So, to learn about the various elements in a periodic table, here are the Modern Periodic Table Trends that each chemistry student should know! These trends and patterns help in identifying the certain properties of an element. Let’s learn the trends to know the various trends and exceptions.
Also read:-
Physical and Chemical Properties of Non-metals
Valency
One of the trends in the modern periodic table is the valency of an atom. The valency of an atom is the number of electrons present in the outermost shell. To determine the valency of an element, one has to simply look at its position in the periodic table. In short, the group in which the element is placed indicates its valency. Here are some examples of the same:
- All alkali metals have the valency one and form monovalent bonds
- The alkali earth metals have two electrons in the last orbit
- Halogens in group 17 have a valency of one (8-7 electrons)
Atomic Size
The second trend in the periodic table is its atomic size. Atomic size is the distance between the centre of the nuclei and its outermost orbit. To simplify, it is the radius of an atom. The atomic size decreases as we move from left to right in a period. The reason for the decrease in size is the increase in the number of electrons hence increasing the nuclear charge. More so, due to stronger nuclear charge, the nucleus pulls the electron closer, reducing the atomic radii and in contrast, moving top to bottom down the group, the atomic size of the elements increases. The reason for the same is that the number of shells of the atom increase, increasing their radii.
Electronegativity
An atom of any element can attract a shared pair of electrons in a chemical bond.
- From left to right across a period, the electronegativity increases
- From top to bottom down a group, the electronegativity decreases
The reason for this trend in the periodic table is that when the number of shells increases down the group, the pull of the nucleus to attract electrons decreases. The most electronegative element is Florine, and the least is Caesium.
Metallic & Non-metallic Properties
While looking at the periodic table, a zigzag line across the table separates the metals from the non-metals. For instance, the metals such as Magnesium, Aluminium, and Iron rest on the left-hand side while the non-metals such as Fluorine and Sulphur rests on the right-hand side. Some examples are Boron, Arsenic, Tellurium.
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