Explanation

• Type: Chemical compound
• Formula: H₂O
• Elements: Hydrogen + Oxygen
• Bond: Covalent bond
• Ratio: 2 hydrogen : 1 oxygen

Last verified on 10-06-2026

Explanation

• Chlorine has the smallest atomic radius among the given elements.
• Atomic radius decreases from left to right across a period.
• Period 3 elements: Sodium (Na), Magnesium (Mg), Aluminum (Al), Chlorine (Cl)
• Atomic radius trend: Na > Mg > Al > Cl
• Reason: Increasing nuclear charge across the period

Last verified 10-06-2026

Explanation

• Ibn Zakariya Al-Razi is considered the father of Pediatrics (Child healthcare).
• He was a famous Muslim physician, philosopher, and scientist.
• Field: Medicine, Chemistry, Philosophy
• Known as: Rhazes
• Famous books: Al-Hawi, Kitab al-Mansuri

Last verified on 09-06-2026

Explanation

Hydrogen gas is H₂, molar mass ≈ 2.016 g/mol  

Moles = mass / molar mass  

= 8.064 g / 2.016 g/mol = 4.0 mol

So there are 4 moles of H₂ molecules.

Last verified on 09-06-2026

Explanation

• Iron (Fe) is a trace element required in very small amounts in the body.
• It is essential for forming hemoglobin in blood.
• It helps in oxygen transport in red blood cells.
• Other trace elements include: Zinc, Copper, Iodine, Manganese, Cobalt.

Last verified on 09-06-2026

Explanation

There are 3 main types of chemical bonds based on electron behavior.

1. Ionic bond → electrons are transferred (lost or gained).
2. Covalent bond → electrons are shared between atoms.
3. Metallic bond → electrons are delocalized (free-moving) in metals.

Last verified on 09-06-2026

Explanation

• Chemical energy is the energy stored in the bonds between atoms and molecules.
• It is released or absorbed during chemical reactions.
• Found in substances like food, fuel, and batteries.
• It is a form of potential energy stored in chemical bonds.
• It changes into other forms like heat or light when reactions occur.

Last verified on 08-06-2026

Explanation

• Sublimation is the direct transition of a solid into a gas without passing through the liquid phase.

Additional information:

Some common sublimating substances:

• Dry ice (CO₂) – solid → gas
• Iodine crystals – solid → violet gas
• Camphor – solid → vapor
• Naphthalene (mothballs) – solid → gas
• Ammonium chloride – solid → gas

Last verified on 13-03-2026

Explanation

• The hardest substance in the world is diamond.
• Its hardness is due to the strong covalent bonding between its carbon atoms.
• This making it the most resistant to scratching.

Additional information:

• Category: Native minerals
• Cleavage: 111 (perfect in four directions)
• Crystal class: Hexoctahedral (m3m); H-M symbol: (4/m 3 2/m)
• Crystal habit: Octahedral
• Crystal system: Cubic
• Dana classification: 1.3.6.1
• Density: 3.5–3.53 g/cm3 3500–3530 kg/m3

Last verified on 07-06-2026

Explanation

• The chemical formula for water is H₂O.

Atomic masses:

• Hydrogen (H) = 1 amu each → 2 × 1 = 2 amu
• Oxygen (O) = 16 amu

Total molecular mass = 2 (from H) + 16 (from O) = 18 amu.

Last verified on 07-06-2026