Acertain metal fluoride crystallizes in such a way that the fluoride ions occupy simple cubic lattice sites, while the metal ions occupy the body centers of half the unit cells. the formula for the metal fluoride is

Explanation:

In a simple cubic lattice lattice, the atoms are present at the eight corners of the cibe.

Since it is mentioned that the fluorine is present at the corners and also 1 corners are shared by 8 unit cells. So, share of atom in one unit cell is:-

Also, the metal, M occupy half of the body centre. A cube has only one body centre. So, share of M in each unit cell:-

Thus, the formula is:-

Or simplifying

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

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