Railway GK Questions 2026

After discovering the electron in 1897, J. J. Thomson pictured the atom as a sphere of positive charge with negatively charged electrons stuck in it, a picture often compared to plums in a pudding or seeds in a watermelon.

Isotopes are atoms of the same element, so they have the same number of protons and therefore the same atomic number, but they carry different numbers of neutrons, which makes their mass numbers differ.

The modern periodic table has seven horizontal rows, called periods, and eighteen vertical columns, called groups.

John Newlands arranged the fifty-six elements known in 1866 in order of increasing atomic mass, beginning with hydrogen, the lightest, and ending with thorium, the fifty-sixth.

Henry Moseley showed in 1913, from the frequencies of the X-rays that elements emit, that the atomic number, the number of protons in the nucleus, is the more fundamental property of an element.

Electronegativity is the tendency of an atom to attract a shared pair of electrons towards itself. It increases from left to right across a period, as nuclear charge grows, and decreases down a group, as each new shell puts the outer electrons further from the nucleus.

The alkali metals are lithium, sodium, potassium, rubidium, caesium and francium. Each has a single electron in its outermost shell, loses it readily to form a positive ion, and therefore stands in group 1 of the modern periodic table.

The capacity of a shell is given by the formula 2n squared, where n is the number of the shell counted outward from the nucleus.

Most alpha particles passed straight through the foil, a few were deflected through small angles and about one in twenty thousand bounced back.

James Chadwick discovered the neutron in 1932 by bombarding beryllium with alpha particles and showing that the radiation produced consisted of neutral particles of nearly the same mass as the proton.

The Greek philosopher Democritus, working in the fifth century before the common era, argued that matter could be divided only up to a limit, and he called that smallest indivisible particle atomos, from which the word atom comes.

A lichen is a partnership of an alga and a fungus and takes its water and nutrients straight from the air, with no protective cuticle and no roots.

A catalytic converter holds platinum, palladium and rhodium on a honeycomb support, which oxidise carbon monoxide and unburnt hydrocarbons to carbon dioxide and water and reduce the oxides of nitrogen to nitrogen.

An electrostatic precipitator gives the dust and ash particles in the flue gas an electric charge as they pass an electrode, and then collects them on plates carrying the opposite charge; the plates are shaken so that the collected ash falls into a hopper.

This Act is the specific law on air pollution. It empowers the Central and State Pollution Control Boards to lay down emission standards for industry and for vehicles, to declare air pollution control areas and to require consent before a polluting plant is set up or operated.

The National Air Quality Index has six bands: 0 to 50 is Good, 51 to 100 Satisfactory, 101 to 200 Moderate, 201 to 300 Poor, 301 to 400 Very Poor and 401 to 500 Severe.

The Montreal Protocol, adopted in 1987 under the Vienna Convention, commits its parties to phasing out chlorofluorocarbons, halons and other chemicals that destroy stratospheric ozone, and it is regarded as the most successful environmental treaty for that reason.

Particulate matter is graded by the diameter of the particles measured in micrometres, so PM10 means particles of ten micrometres or less and PM2.5 means particles of 2.5 micrometres or less, which is about thirty times finer than a human hair.

Sulphur dioxide from industry and traffic around Agra is oxidised in the air and comes down as sulphuric acid, which attacks the calcium carbonate of marble.

Sulphur dioxide, released when coal and oil containing sulphur are burnt, is oxidised in the atmosphere to sulphur trioxide, which dissolves in water droplets to give sulphuric acid.