Write true or false for the statements: Non-metals are electronegative. They tend to form bonds by gaining electrons. As the trends in the electronegativity show,non-metals are found on the right-hand side of the periodic table towards the top.

Which group of elements could be placed in Mendeleev's Periodic Table without disturbing the original order? Give reason.

The electrons in the atoms of four elements $A, B, C$ and $D$ are distributed in three shells having $1, 3, 5$ and $7$ electrons in the outermost shell respectively. State the period in which these elements can be placed in the modern periodic table. Write the electronic configuration of the atoms of $A$ and $D$ and the molecular formula of the compound formed when $A$ and $D$ combine.

Arrange the following elements in the order of their decreasing metallic character:
$Na, Si, Cl, Mg, Al$

Which of the following is the outermost shell for elements of period $2$?

Mention any two trends exhibited by elements when we go from left to right across the period of the periodic table.