Answer:
Beryllium
Explanation:
The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).
The alkaline earth metals are all of the elements in the second column (column 2A) of the periodic table.
They all have 2 valence electrons in their outermost she'll.
Therefore the one in period two is Beryllium because it has atomic number 4 , that is 4 electrons.
This means it's electronic configuration using KLMN method is 2:2 making it to be in period 2.
Beryllium is a chemical element with the symbol Be and atomic number 4. It is a relatively rare element in the universe, usually occurring as a product of the spallation of larger atomic nuclei that have collided with cosmic rays.
Beryllium is a steel-gray metal that is quite brittle at room temperature, and its chemical properties somewhat resemble those of aluminum. It does not occur free in nature. Beryllium is found in beryl and emerald, minerals that were known to the ancient Egyptians.
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