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Which of the following metals CANNOT be cut with a knife?
Sodium
Copper
Lithium
Potassium
Copper
Sodium is an alkali metal (Group 1 of the periodic table) known for being extremely soft. Because of its low metallic bonding strength and high malleability, it can be easily cut with a knife.
Sodium is an alkali metal (Group 1 of the periodic table) known for being extremely soft. Because of its low metallic bonding strength and high malleability, it can be easily cut with a knife.
Cutting sodium feels remarkably similar to slicing through firm butter or a piece of cheese with a kitchen knife.
Remember 'So Soft Sodium' тАФ Alkali metals are so soft you can cut them with a knife.
Group1: Li,Na,K,Rb,Cs тАФ Alkali metals with low hardness
Transition┬аMetals: Cu,Fe,Zn тАФ High tensile strength and hardness
Alkali metals like sodium (Na), potassium (K), and lithium (Li) have a single valence electron resulting in weak metallic bonding compared to transition metals like copper (Cu) or iron (Fe). Consequently, they possess extremely low hardness and can be readily sliced with a sharp blade.
Sodium (Na) is stored under kerosene oil to prevent accidental reactions with moisture and oxygen in the air.
Copper (Cu) is a transition metal known for high electrical conductivity, ductility, and hardness.
Lithium, sodium, and potassium are soft enough to be cut using a knife or razor blade.
Transition metals like copper, iron, and aluminum have very strong metallic bonding.
Understanding periodic table trends helps predict physical properties of elements.
Sodium is used in chemical synthesis and as a coolant in nuclear reactors.
Copper is widely used in electrical wiring and plumbing.
| Feature | Sodium (Na) | Copper (Cu) |
|---|---|---|
Hardness | Very soft (can be cut with knife) | Hard (cannot be cut with knife) |
Classification | Alkali Metal (s-block) | Transition Metal (d-block) |
Option A (Sodium), Option C (Lithium), and Option D (Potassium) are all soft alkali metals that can be cut with a knife.
Option B (Copper) is a transition metal with high hardness and strength, making it impossible to cut with a normal knife.
B is correct тАФ Copper is a hard transition metal and cannot be cut with a knife, whereas sodium, lithium, and potassium are soft alkali metals.
Always remember that s-block alkali metals (Group 1) are exceptionally soft and have low melting points compared to d-block transition metals.
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