Why does the basic character decrease along a period? Give reasons.

Write true or false for the statement: Electronic configuration of hydrogen resembles that of alkaline earth metals.

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

The elements $Be$,$Mg$,and $Ca$,each having two electrons in their outermost shells,are in periods $2$,$3$,and $4$ respectively of the modern periodic table. Answer the following questions,giving justification in each case:
$(i)$ Write the group to which these elements belong.
$(ii)$ Name the least reactive element.
$(iii)$ Name the element having the largest atomic radius.

Name the following:
$(a)$ $A$ metal that can be cut with a knife.
$(b)$ $A$ metal that is liquid at room temperature.
$(c)$ $A$ metal that has $3$ valence electrons.

Which of the following are the characteristics of isotopes of an element?
$(i)$ Isotopes of an element have same atomic masses
$(ii)$ Isotopes of an element have same atomic number
$(iii)$ Isotopes of an element show same physical properties
$(iv)$ Isotopes of an element show same chemical properties