Which property decreases from left to right across the periodic table and increases from top to bottom?
(i) Atomic radius
(ii) Electronegativity
(iii) Ionisation energy
(iv) Metallic character

Options

A. (i) only
B. (i) , (ii) and (iii)
C. (i), (iii) and (iv)
D. (i) and (iv)

Explanation

To determine which property decreases from left to right across the periodic table and increases from top to bottom, we will analyze each of the given properties: atomic radius, electronegativity, ionization energy, and metallic character.

### Step 1: Analyze Atomic Radius
- **Definition**: Atomic radius is the distance from the nucleus to the outermost shell of an electron.
- **Trend Across Periods**: As we move from left to right across a period, the atomic radius decreases. This is because the number of protons in the nucleus increases, leading to a greater nuclear charge that pulls the electrons closer to the nucleus.
- **Trend Down Groups**: As we move down a group, the atomic radius increases. This is due to the addition of electron shells, which outweighs the increase in nuclear charge.

### Step 2: Analyze Electronegativity
- **Definition**: Electronegativity is the ability of an atom to attract electrons in a chemical bond.
- **Trend Across Periods**: Electronegativity increases from left to right across a period because the increasing nuclear charge attracts the bonding electrons more strongly.
- **Trend Down Groups**: Electronegativity decreases down a group due to the increased distance between the nucleus and the valence electrons, which reduces the attraction.

### Step 3: Analyze Ionization Energy
- **Definition**: Ionization energy is the energy required to remove an electron from an atom.
- **Trend Across Periods**: Ionization energy increases from left to right across a period due to the increased nuclear charge, which holds the electrons more tightly.
- **Trend Down Groups**: Ionization energy decreases down a group because the outer electrons are further from the nucleus and are shielded by inner electrons, making them easier to remove.

### Step 4: Analyze Metallic Character
- **Definition**: Metallic character refers to the tendency of an element to lose electrons and form positive ions.
- **Trend Across Periods**: Metallic character decreases from left to right across a period as elements become more non-metallic.
- **Trend Down Groups**: Metallic character increases down a group because the outer electrons are further from the nucleus and are more easily lost.

### Conclusion
From the analysis:
- **Atomic radius**: Decreases across a period, increases down a group.
- **Electronegativity**: Increases across a period, decreases down a group.
- **Ionization energy**: Increases across a period, decreases down a group.
- **Metallic character**: Decreases across a period, increases down a group.

The property that **decreases from left to right across the periodic table and increases from top to bottom** is **metallic character**.

### Final Answer
(iv) Metallic character