Question

Sodium--reacts vigorously with cold water.
A. Metal
B. Amalgam
C. In the molten state
D. None of the above

Answer 1

Hint: To answer this question we should know what the block from which sodium belongs. By the block we can determine that it is a metal or nonmetal. Sodium is an s-block element. Top left part of the periodic table contains s-block elements.

Complete answer:
The top left of the periodic table contains the metals only. Metals tend to lose electrons. So, their reactivity is compared on the basis of electron-donating power. Sodium is a s-block element, so it is a metal.

The electronegativity of the alkali metals are least and along the period, due to largest size, and small effective nuclear charge alkali metal can lose electrons easily so, the alkali metals are most reactive. So, sodium is a very reactive metal.

As we go down in a group the size of the metal increases. Down in the group, the electrons get added in the next higher shell, so the distance between the nucleus and outermost shell electrons increases, so the attraction of the nucleus on the outermost shell decreases. So, reactivity of metal decreases. So, sodium metal reacts vigorously with cold water.

Therefore, option (A) metal is the correct answer.

Note: As we move left to right in the periodic table, reactivity to lose electrons decreases, and the reactivity to accept electrons increases. So, left to right in the periodic table, the reactivity of metals decreases, and the reactivity of the non-metals increases. Electronegativity also increases left to right in the periodic table.