Chemistry in Class 9 Science : Practice MCQ Questions & Answers with Explanations

Hydrogen, oxygen, and carbon all have isotopes with different numbers of neutrons.

Atomic spectra are produced when electrons transition between energy levels.

The third shell can hold a maximum of 18 electrons.

Plastic is an insulator and does not conduct electricity.

Dalton's model considered atoms indivisible, which was later disproved.

An atom with equal numbers of protons and electrons is electrically neutral.

One atomic mass unit is defined as one-twelfth the mass of a carbon-12 atom.

Electrons move in orbitals outside the nucleus and carry a negative charge.

Sodium has one electron in its outermost shell.

In beta decay, the mass number remains unchanged because a neutron changes into a proton.

A neutron has a mass approximately equal to 1 atomic mass unit (amu).

Acid-base neutralization produces salt and water.

Mass is neither created nor destroyed during a chemical reaction.

The molar mass of CO₂ is 44 g/mol.

A covalent bond is formed by sharing electrons between atoms.

Calcium chloride contains one calcium atom and two chlorine atoms.

Neon is a noble gas and is chemically inert.

Oxygen, nitrogen, and chlorine all exist as diatomic molecules.

The empirical formula represents the simplest whole-number ratio of atoms in a compound.

Oxygen molecules consist of two oxygen atoms bonded together.