CHEM-1

Atomic number

The number of protons in an atom.

Mass number

The total number of protons and neutrons in an atom.

Isotopes

Atoms of the same element with different numbers of neutrons.

Group 1 elements

Alkali metals that are very reactive, soft, with low melting points.

Group 7 elements

Halogens, which are reactive non-metals that form salts.

Group 0 elements

Noble gases that are unreactive and have a full outer shell.

Ionic bonding

A bond formed between a metal and a non-metal where electrons are transferred.

Covalent bonding

A bond between two non-metals where electrons are shared to form molecules.

Metallic bonding

A bond where metal atoms share delocalised electrons, creating strong bonds with high melting points.

Combustion reaction

A reaction involving burning in oxygen.

Neutralisation reaction

A reaction where an acid and a base react to form salt and water.

Displacement reaction

A reaction in which a more reactive element replaces a less reactive one.

Decomposition reaction

A reaction where a compound breaks down into simpler substances.

Litmus indicator

An indicator that turns red in acid and blue in base.

Universal indicator

An indicator that shows a full color range based on pH; strong acid appears red and strong base appears purple.

Mole

A unit that is equal to 6.022 × 10²³ particles.

Molar mass

The mass of one mole of a substance, numerically equal to its relative atomic or molecular mass in grams.

Positive ion

An ion that loses electrons and has more protons than electrons.

Negative ion

An ion that gains electrons and has more electrons than protons.