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1:these are metalloids.
2:Modern periodic table is based on the concept of atomic number . "The chemical and physical properties of elements are the periodic functions of their atomic numbers and electronic configurations."
3:b
4: Sodium.
k l m n
2 8 1
5:All of the elements in a period have the same number of atomic orbitals. For example, every element in the top row (the first period) has one orbital for its electrons. All of the elements in the second row (the second period) have two orbitals for their electrons.
6:Both magnesium and Calcium are alkaline earth metals,Which means that they form strong alkalis when the react with water. on further speaking they are of the same valency 2, they have only two electrons in the valence shells, and there da almost same nature.
7:The major difference is that the elements in Mendeleev's periodic table were arranged by atomic mass and the modern periodic table arranges elements by atomic number. Of course as elements are constantly being discovered there were significantly fewer elements in Mendeleev's periodic table.
8:: The properties of elements depend upon valence electrons in the atom which in turn depends on the total number of electrons, i.e., atomic number. Therefore, atomic number is a more appropriate parameter than atomic mass for classification of elements.
Metallic character decreases as you move across a period in the periodic table from left to right.
Metallic character increases as you move down an element group in the periodic table.
9:a k l m n
2 8 8 2, it's valency is 2
b non metal
c Ca2+Cl gives CaCl2
d Calcium is more reactive than magnesium because the calcium atom is larger than the magnesium atom.
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