In the modern periodic table , the element calcium (atomic number=20) is surrounded by elements with atomic number 12,19,21 and 38, which of those elements has physical and chemical properties resembling those of calcium?

The calcium atomic number is 20, and it is located in Group 2 of the modern periodic table. Elements within the same group share similar chemical and physical properties due to having the same number of valence electrons.

Let us analyze the elements surrounding calcium:

• Atomic Number 19: Potassium is an element of Group 1. Since it belongs to a different group, its properties are not similar to calcium.
• Atomic Number 21: Scandium belongs to Group 3 and does not share the same chemical and physical properties as calcium due to having a different number of valence electrons.
• Atomic Number 12: Magnesium is in Group 2, the same group as calcium. This means it has similar chemical and physical properties as calcium because both elements have 2 valence electrons.
• Atomic Number 38: Strontium is also in Group 2. Like magnesium, it resembles calcium in chemical and physical properties due to the same number of valence electrons (2).

In conclusion, the elements with atomic numbers 12 (magnesium) and 38 (strontium) have properties that closely resemble those of calcium. The calcium atomic number places it in Group 2, and elements in this group all have 2 valence electrons, which is the primary factor determining their similar behavior.

This alignment with magnesium and strontium showcases how the calcium atomic number determines its group placement and the resulting similarities in chemical and physical properties within the periodic table.