Question

The modern periodic table consists of 18 groups and 7 periods. what is the atomic number of the element placed in the 3rd group and the 4th period

Answer 1

Atomic No. 21
Sc
Scandium
Atomic mass 45.0

Answer 2

Answer: The element belonging to Group 3 and Period 4 of the periodic table is Scandium.

Explanation:

Modern periodic table is arranged according to increasing atomic numbers.

Elements are arranged in 7 horizontal rows known as periods and 18 vertical columns known as Groups.

The element that is placed in Group 3 and Period 4 of the periodic table is Scandium. The atomic number of this element is 21.

The electronic configuration of this element = $1s^22s^22p^63s^23p^64s^23d^1$

Hence, the element is Scandium.