Question

Which trend occurs across the period from sodium to argon?
A. A change from metal to non-metal
B. An increase in melting point
C. A more violet reaction with water
D. An increase in electrical conductivity

Answer 1

Hint – The metallic character of an element in the third period of the periodic table decreases as we move right across the period. This property of the period can be used to figure out the trend that occurs across the period from sodium to argon.

Complete step-by-step answer:
As we know that both sodium and argon are present in the period 3 of the periodic table. Between Sodium and Argon there are several other elements like Magnesium, Aluminium, Silicon, Phosphorus, Sulphur and Chlorine, the metallic character of these elements decrease as we move across the period.
The elements – sodium, Magnesium and Aluminium are considered to be metals, Silicon is considered to be a semi-metal or also a metalloid and the rest of the elements that is Phosphorus, Sulphur, Chlorine and argon are considered to be non-metals.
Thereby indicating that the change of metallic nature or the trend observed in the metallic character for this period from sodium element to the argon element is that from metal to non metal.
Hence the correct option is option (A) that is “A change from metal to non-metal”

Note: As we saw that in the period 3 of the periodic table elements on the left are metals and so elements on the right side are non-metals some extra points to remember about this period are that the;
1. Melting points change from high to low as we move across the period.
2. Boiling points change from high to low as we move across the period.
3. Electrical and heat conductors on the left to insulators on the right
4. Metallic lustre on the left to dull on the right as we move across the period.
5. Colour changes from grey on the left to coloured on the right (except argon which is colourless) as we move across the period.