Assuming that elements are formed to complete the seventh period, what would be the atomic number of the alkaline earth metal of the eighth period?

Options

A. 113
B. 120
C. 119
D. 106

Answer

To determine the atomic number of the alkaline earth metal in the hypothetical eighth period of the periodic table, we can follow these steps:

### Step 1: Understand the Periodic Table Structure
The periodic table is organized into periods and groups. Each period corresponds to a row in the table, and each group corresponds to a column. The alkaline earth metals are located in Group 2 of the periodic table.

### Step 2: Identify the Number of Elements in Each Period
We know the number of elements in each of the existing periods:
- 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: Calculate the Atomic Numbers for Each Period
Starting from the first period:
- Period 1:
- Atomic number 1 (H)
- Atomic number 2 (He)

- Period 2:
- Atomic number 3 (Li) to atomic number 10 (Ne) → 8 elements

- Period 3:
- Atomic number 11 (Na) to atomic number 18 (Ar) → 8 elements

- Period 4:
- Atomic number 19 (K) to atomic number 36 (Kr) → 18 elements

- Period 5:
- Atomic number 37 (Rb) to atomic number 54 (Xe) → 18 elements

- Period 6:
- Atomic number 55 (Cs) to atomic number 86 (Rn) → 32 elements

- Period 7:
- Atomic number 87 (Fr) to atomic number 118 (Og) → 32 elements

### Step 4: Hypothetically Extend to the Eighth Period
If we were to extend to an eighth period, we would add 32 more to the last atomic number of period 7 (which is 118):
- Atomic number of the first element in Period 8 = 118 + 32 = 150

### Step 5: Identify the Alkaline Earth Metal in the Eighth Period
The alkaline earth metals are located in Group 2. Therefore, the first alkaline earth metal in the eighth period would be the second element in this period:
- Atomic number of the alkaline earth metal in Period 8 = 150 + 1 = 151

### Conclusion
Thus, the atomic number of the alkaline earth metal in the hypothetical eighth period would be **151**.

---