Explanation

• As you move down a group in the periodic table, the atomic size increases.
• This means that the outermost electrons are farther away from the nucleus, making it easier for the atom to gain an extra electron.
• As a result, the electron affinity decreases down a group.

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.

Explanation

• Henry Moseley's famous work in 1913 showed that the chemical properties of elements are a periodic function of their atomic number (Z), not their atomic mass.
• This discovery led to the modern periodic table, where elements are arranged in order of increasing atomic number (Z), rather than atomic mass.

Explanation

The elements in group VIIA of the periodic table are called halogens.

This group consists of the following elements:

• Fluorine (F)
• Chlorine (Cl)
• Bromine (Br)
• Iodine (I)
• Astatine (At)
• Tennessine (Ts)

Explanation

• The 4th and 5th periods in the periodic table are known as the long periods.
• These periods contain 18 elements each, making them the longest periods in the periodic table.

Important Points:

• Short periods: 1st and 2nd periods (2 and 8 elements, respectively)
• Long periods: 4th and 5th periods (18 elements each)
• Normal periods: 3rd and 6th periods (8 and 12 elements, respectively)

Explanation

The periodic table divided into S, P, d, and f block based on Electronic Configuration.

• S block: The s block includes the first two columns of the periodic table, which are the alkali and alkaline earth metals.
• P block: The p block includes the elements in the six columns on the right side of the periodic table.
• D block: The d block includes the elements in the ten columns in the middle of the periodic table. These are also known as the transition metals.
• F block: The f block includes the elements at the bottom of the periodic table, which are known as the inner transition metals or lanthanides and actinides.

Explanation

• In 1869, Dmitri Mendeleev proposed his periodic law, which states: "When the elements are arranged in order of increasing atomic mass, certain sets of properties recur periodically."
• This law allowed him to create the first periodic table, where elements were arranged in a logical order based on their atomic masses and chemical properties.

Explanation

• Gamma rays are commonly used for sterilization of medical instruments.
• Because of their high energy and penetrating power, which allows them to effectively kill bacteria and other microorganisms.
• Gamma radiation is also used to sterilize medical supplies.
• Such as syringes, gloves, and implantable devices.

Explanation

• In Rutherford's famous experiment, known as the "Gold Foil Experiment" or "Rutherford's Scattering Experiment", a thin layer of zinc sulphide (ZnS) was used as the screen to detect the scattered alpha particles.
• Zinc sulphide is a phosphor that emits light when struck by radiation, allowing Rutherford to visualize the trajectory of the alpha particles.

Explanation

• De Broglie extended the wave-particle duality to electrons in 1923.
• He proposed that particles such as electrons exhibit wave-like properties.
• A hypothesis that was later confirmed experimentally and became a fundamental concept in quantum mechanics.