Multiple-Choice Questions (MCQs)
1. Which of the following elements has the highest electronegativity?
Answer: F
Fluorine is the most electronegative element.
2.The number of valence electrons in carbon is:
Answer: 4
3. Which period contains elements with 3 electron shells?
Answer: Period 3
4. Which group in the periodic table is known as the noble gases?
Answer: Group 18
5. Which of the following has the largest atomic radius?
Answer: Rb
Atomic radius increases down the group.
6. The element with atomic number 12 belongs to:
Answer: Magnesium
7. Which element is a metalloid?
Answer: Silicon
8. Which element has the electron configuration 1s² 2s² 2p⁵ ?
Answer: Fluorine
9. What is the valency of nitrogen?
Answer: 3
10. Which of the following increases across a period (left to right)?
Answer: Electronegativity
II. Short Answer Questions
1. State the Modern Periodic Law.
Answer:
The physical and chemical properties of elements are periodic functions of their atomic number.
2. Why does atomic radius decrease across a period?
Answer:
Across a period, the number of protons increases → greater nuclear charge → electrons are pulled closer → atomic radius decreases.
3. Why are noble gases inert?
Answer:
They have a complete valence shell, making them stable and unreactive.
4. Define ionization energy.
Answer:
The energy required to remove the most loosely bound electron from an isolated gaseous atom.
5.Why is the size of a cation smaller than its parent atom?
Answer:
A cation loses electrons → reduced electron-electron repulsion → nucleus pulls electrons closer → smaller radius.
III. Long Answer Questions
1. Explain the trends of electronegativity in the periodic table.
Answer:
-
Across a period: Electronegativity increases due to increasing nuclear charge and decreasing atomic radius.
-
Down a group: Electronegativity decreases because atomic size increases and the nucleus is farther from valence electrons.
2. Compare metals, non-metals, and metalloids with examples.
Answer:
| Property | Metals | Non-Metals | Metalloids |
|---|---|---|---|
| Conductivity | Good | Poor | Moderate |
| State | Mostly solids | Solid/liquid/gas | Solids |
| Luster | Shiny | Dull | Semi-shiny |
| Examples | Fe, Cu | O₂, S | Si, Ge |
Answer:
Ionization energy decreases down a group because:
-
More electron shells are added → increased atomic radius.
-
Valence electrons are farther from the nucleus.
-
Shielding effect increases → nucleus has less hold on outer electrons.
