Which of the following sets of elements has the same valency?

Valency is determined by the number of electrons in an element's outermost shell, which dictates its chemical bonding capacity [2]. Elements in the same group of the periodic table typically exhibit the same valency. Magnesium (Mg), Calcium (Ca), and Barium (Ba) all belong to Group 2, known as the alkaline earth metals [3]. According to their electronic configurations, Magnesium (2, 8, 2) and Calcium (2, 8, 8, 2) both possess two valence electrons, giving them a valency of 2 [3]. Barium, being further down in the same group, also shares this characteristic valency of 2 [3]. In contrast, Sodium (Na) and Potassium (K) are Group 1 elements with a valency of 1, while Aluminium (Al) is a Group 13 element with a valency of 3 [3]. Therefore, only the set Mg, Ca, and Ba has the same valency.

Sources

1. [2] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > 3.3 HOW DO METALS AND NON-METALS REA ALS REACT? > p. 47
2. [3] https://www.energy.gov/sites/prod/files/2020/07/f76/The%20Periodic%20Table%20of%20Elements.pdf