Explanation

• Rutherford’s gold foil experiment (1911) showed that an atom has a small, dense, positively charged center called the nucleus.
• The mass of the atom is concentrated in the nucleus, while most of the atom is empty space.

Additional information:

• Nucleus contains: Protons (+) and neutrons (neutral)
• Electrons move around the nucleus in mostly empty space
• The experiment involved alpha particles being deflected by the nucleus.

Last verified on 10-02-2026

Explanation

• Mercury is the only elemental metal that at room temperature is Liquid.
• Mercury (Hg) is the only metal that remains liquid at room temperature (about 25°C).

Additional information:

• Chemical Symbol: Hg
• Atomic Number: 80
• Melting Point: −38.83°C
• Boiling Point: 356.73°C

Last verified on 20-07-2026

Explanation

• Carbon Dating is one of the methods to calculate the age of fossils. It is based on the principle of Radioactivity.
• Radioactive isotope: Carbon-14 (¹⁴C)
• Half-life: 5,730 years
• Developed by: Willard Libby
• Introduced: 1949
• Dating range: Up to 50,000 years

Last verified on 20-07-2026

Explanation

• Noble gases are called inert gases because their outermost electron shell is complete.
• They are located in Group 18 of the periodic table.
• Due to their stable electronic configuration, they show very little chemical reactivity.
• Noble gases are colorless, odorless, and monoatomic under normal conditions.
• They are used in neon signs, electric bulbs, lasers, welding, and balloons (helium).

Last verified on 19-07-2026

Explanation

• The instrument used to measure temperature is called a thermometer.
• A thermometer shows how hot or cold an object or place is.

Additional information:

• Barometer measures air pressure.
• Hygrometer measures humidity (moisture in air).

Last verified on 16-06-2026