Fill in the blanks: [1 x 5 = 5 Marks]
Across a period from left to right in Modern Periodic table-
Number of electron shells _______________, number of valence electrons ______________, Character of
elements change form _______________ to _________________. In this metals will form ___________
oxides and non metals will form ____________ oxides.
Down the group in the modern periodic table:
Number of electron shells _______________, number of valence electrons ______________, the reactivity
____________ in metals and ___________ in non-metals.
Answers
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On moving from left to right in a period, the chemical reactivity of elements first decreases and then increases. On moving from left to right in a period, the number of valence electrons increases from 1 to 8. On moving from left to right in a period, the atomic size decreases; the size of the atoms decreases. Since the atomic size decrease when we move from left to right in a period, therefore, electronegativity increases in moving left to right. Atomic size increases when moving down in a group thus electronegativity decreases when we move from top to bottom in the periodic table.
Metallic character decreases as you move across a period in the periodic table from left to right. This occurs as atoms more readily accept electrons to fill a valence shell than lose them to remove the unfilled shell.