Which of the following statements about valence electrons and the periodic table is true? The number of valence electrons decreases from left to right across each period. The number of valence electrons increases from top to bottom within each group. All of the elements in group 9 have nine valence electrons. Elements with the most valence electrons are in group 18.
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ANSWER
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.
last one is false and all are true