Numerous forms of the periodic table have been devised from time to time. A modern version, which is most convenient and widely used is the long or extended form of periodic table. The horizontal rows are called periods. There are altogether seven periods. The first period consists of 2 elements. The subsequent periods consist of 8, 8, 18, 18 and 32 elements respectively. Elements having similar outer electronic configurations in their atoms are grouped in vertical columns. These are referred to as groups or families. According to the recommendation of IUPAC, groups are numbered 1 to 18 replacing the older notation of group 0,IA, IIA, ....VIIA, VIII, IB, ......VIIB
An element belongs to group 17. It is present in third period and its atomic number is 17. What is the atomic number of the element belonging to same group and present in fifth period?

Options

A. 25
B. 33
C. 35
D. 53

Explanation

To find the atomic number of the element that belongs to group 17 and is present in the fifth period, we can follow these steps:

### Step 1: Identify the Element in the Third Period
The question states that we have an element in group 17 (the halogens) and in the third period with an atomic number of 17. This element is Chlorine (Cl).

### Step 2: Determine the Position of the Element in the Fifth Period
Next, we need to find the element that is also in group 17 but in the fifth period. The periods in the periodic table are as follows:
- Period 1: 2 elements
- Period 2: 8 elements
- Period 3: 8 elements
- Period 4: 18 elements
- Period 5: 18 elements
- Period 6: 32 elements
- Period 7: 32 elements

### Step 3: Count the Elements in the Groups
In the periodic table, each group contains one element from each period. Since we know that group 17 contains:
- Period 3: Chlorine (Cl) with atomic number 17
- Period 4: Bromine (Br) with atomic number 35
- Period 5: Iodine (I) with atomic number 53

### Step 4: Find the Atomic Number of the Element in the Fifth Period
From the information above, we can conclude that the element in group 17 and in the fifth period is Iodine (I), which has an atomic number of 53.

### Final Answer
The atomic number of the element belonging to group 17 and present in the fifth period is **53**.

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