Answer:
D. Noble gases
Explanation:
- Noble gases are elements in the last group of the periodic table.
Why are they the least reactive elements?
- Noble gases have an octet configuration, which means they have maximum number of electrons in their outermost energy levels.
- This makes them stable, which means they are inert.
- Examples of noble gases include neon, argon, krypton, etc.
What is the Trend in reactivity in the periodic table?
Down the group from top to bottom
- The reactivity of metals in the periodic table increases down the group due the increase in the number of energy levels which makes it easier for them to lose electron(s).
- Non-metals react by gaining electron(s), therefore, their reactivity decreases down the group because as the energy level increases the nuclear charge decreases.
Across the period from left to right.
- Reactivity of metals decreases across the period because of an increase in nuclear charge which makes it more difficult for them to lose electron(s).
- On the other hand, reactivity of non-metals increases across the period due to increased nuclear charge that makes it easier for them to gain electron(s).
