Select all that apply. what is common about the elements of a period? they have the same number of electron shells. they have similar chemical characteristics. they have similar physical characteristics. they transition from a metal to noble gas.

Answer : The correct options are,

They have the same number of electron shells.

They transition from a metal to noble gas.

Explanation :

Periods : A row in the periodic table is know as periods.

The common features about the elements of a period are :

Groups : A column in the periodic table is know as groups.

The common features about the elements of a same group are :

Hence, the correct options are,

They have the same number of electron shells.

They transition from a metal to noble gas.

Explanation:

In a period, the row number of elements determine the number of shells present in the elements.

For example, elements present in row 3 will have n = 3.

This means that each element of row 3 will have 3 shells. Like sodium is a row 3 element and its electronic configuration is .

Hence, here n = 3.

Also, on moving left to right across a period elements are transitioning from metals to noble gases.

On the other hand, elements present in the same group will have same number of valence electrons.

For example, fluorine and chlorine are both halogen atoms and both of them have only 1 valence electron.

Thus, we can conclude that common about the elements of a period are as follows.

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