The modern periodic table consists of 18 groups and 7 periods. What is the atomic number of the element placed in the 2nd group and the 4th period?
- A20
- B22
- C18
- D10
Solution & Step-by-step Explanation
Let's trace the element in the 2nd group (Alkaline Earth Metals) across the periods:
Period 1: No element in Group 2.
Period 2: Beryllium (Be, Atomic number = 4)
Period 3: Magnesium (Mg, Atomic number = 12)
Period 4: Calcium (Ca, Atomic number = 20)
Thus, the element placed in the 2nd group and 4th period is Calcium with an atomic number of 20.
Period 1: No element in Group 2.
Period 2: Beryllium (Be, Atomic number = 4)
Period 3: Magnesium (Mg, Atomic number = 12)
Period 4: Calcium (Ca, Atomic number = 20)
Thus, the element placed in the 2nd group and 4th period is Calcium with an atomic number of 20.