Explanation

 Angle in radians (θ) = Arc Length / Radius  

θ = 4 m / 2 m = 2 radians

So, the angle made at the center is 2 rad

Explanation

 To calculate the bond order of O2²⁻, we need to construct a molecular orbital diagram.

The molecule has 18 electrons (12 from oxygen atoms and 6 from the negative charge).

These electrons are filled into the orbitals, starting from the lowest energy level. 

Explanation

When atomic orbitals (like s and p) mix to form hybrid orbitals (e.g., sp³, sp², sp),

The resulting orbitals have the same energy — they are degenerate.

This uniform energy level allows for equal bond strength and geometry, such as in methane (CH₄) with four sp³ orbitals.

Explanation

White phosphorus is highly toxic and reactive.

It can ignite spontaneously in air and is harmful to the liver and kidneys.

It’s the most dangerous form of phosphorus.

Explanation

The mass of a nucleus is always less than the sum of the masses of its constituent nucleons.

This difference in mass is known as the "mass defect".

When nucleons come together to form a nucleus, they release energy in the form of binding energy.

According to Einstein's famous equation E=mc², this energy released corresponds to a decrease in mass. 

Explanation

Coal can be converted to petroleum through the Fischer-Tropsch process. 

The Fischer-Tropsch process is a series of chemical reactions

That converts carbon monoxide and hydrogen (syngas) into liquid hydrocarbons, which can be used as a substitute for petroleum. 

Explanation

The ozone layer is a region within the stratosphere, extending from about 15 to 30 km (9 to 19 miles) above the Earth's surface.

It contains a high concentration of ozone (O3), a molecule made up of three oxygen atoms. 

The ozone layer plays a crucial role in protecting the Earth from harmful ultraviolet (UV) radiation from the sun, particularly UV-C and UV-B rays.

Explanation

• A solution that contains a solid solute dissolved in a liquid solvent is called a solid-in-liquid solution or a solute-solvent solution.
• This is the most common type of solution, where a solid substance (the solute) is dissolved in a liquid substance (the solvent).

Explanation

• At room temperature, most ionic compounds are crystalline solids, meaning they have a rigid and orderly crystal structure.
• This is because the strong electrostatic forces between the oppositely charged ions hold them in a fixed position, creating a three-dimensional lattice.

Explanation

• Electronegativity is the ability of an atom to attract a shared pair of electrons in a covalent bond.
• It measures the ability of an atom to pull electrons towards itself.