What do Periods on the Periodic Table represent? (Quick Ans)

The periods on the Periodic table represents the number of shells (or orbits) of an atom.

For example, 

Period 1 represents that the elements lying in that period have only 1 orbit.

what do periods on the periodic table represent, how many shells does hydrogen have, how many shells does helium have (orbits or shells in period 1)

There are 2 elements in the first period i.e hydrogen (H) and helium (He).

These elements have only 1 electron orbit.

how many shells does hydrogen have, how many shells does helium have

Similarly, period 2 represents that the elements lying in that period have 2 orbits.

how many shells does lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon have (orbits or shells in period 2)

Here you can see that all the 8 elements of the second period have 2 orbits.

how many shells does lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon have

In other words, the electrons of period 2 elements are filled up to the 2nd energy shell (or energy orbit).

Similarly, 

Period 3 elements have 3 orbits.

how many shells does sodium, magnesium, aluminum, silicon, phosphorous, sulfur, chlorine, argon have (orbits or shells in period 3)

Period 4 elements have 4 orbits.

electron shells in period 4

Period 5 elements have 5 orbits.

electron shells in period 5

Period 6 elements have 6 orbits.

electron shells in period 6

Period 7 elements have 7 orbits.

electron shells in period 7

(Note: Lanthanides and Actinides are the part of period 6 and Period 7 respectively, but they are placed at the bottom of the Periodic table in order not to distort the shape of Periodic Table)

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Do elements in the same period have similar properties?

NO (for main group elements)

The elements in the same Period do not have the same properties.

Reason?

Let’s take elements of period 2.

period 2 elements

As we move from left to right across a period, the number of orbits remains the same. 

But one more electron is successive added in the outermost orbit of each next element of the same period.

valence electrons of lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine and neon

Because of this reason, their chemical properties differ.

The first element of Period 2 is Lithium (Li) which has 1 electron in outermost orbit. 

Then second is beryllium (Be) which has 2 electrons in outermost orbit.

Similarly, 

Boron has 3 valence electrons

Carbon has 4 valence electrons, 

Nitrogen has 5 valence electrons, 

Oxygen has 6 valence electrons, 

Fluorine has 7 valence electrons and 

Neon has 8 valence electrons. 

Thus, these elements of the same period have different valence electrons, which results in different chemical properties.

Hence, the elements of the same period do not show similar properties.

Also, you might be knowing that the elements on the left side of the Periodic table show metallic nature, while elements on the right side show non metallic nature.

Read the awesome explanation on: Metallic and Nonmetallic character trend in Periodic table.

Also visit: What does the group number tell you?

Exceptions

Mostly, the elements of the same period show different characteristics.

But for d-block elements of the same period, they show somewhat similarities in their properties.

And the f-block elements lying in the same period even show more similarities in the physical and chemical properties.

So this is it for this article.

I hope you have got your concepts clear through this article.

If you have any queries, leave a comment below.

Also let me know, has this article helped you or not? 

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