Chemistry: Periodic Classification Of Elements! Test

Explanation
In the modern periodic table, periods are the horizontal rows and groups are the vertical columns. Periods represent the number of energy levels an atom has, while groups represent the number of valence electrons an atom has. Therefore, the arrangement of periods and groups in the periodic table indicates the arrangement of elements in rows and columns.

Explanation
The third period of the periodic table contains 8 elements. To determine how many of these elements are non-metals, we need to refer to the periodic table. Going from left to right in the third period, the elements are sodium (Na), magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), chlorine (Cl), and argon (Ar). Out of these, sodium, magnesium, aluminum, and silicon are metals, while phosphorus, sulfur, chlorine, and argon are non-metals. Therefore, there are 5 non-metals in the third period.

Explanation
The element that is an essential constituent of all organic compounds belongs to the 14th group. This is because the 14th group elements, also known as the carbon group, consist of carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb). Carbon is particularly important as it forms the backbone of organic compounds due to its ability to form strong covalent bonds with other elements. Therefore, the correct answer is the 14th group.

Explanation
Bauxite can be termed as an ore because it is a naturally occurring mineral that contains a high concentration of aluminum. It is economically viable to extract aluminum from bauxite, making it a valuable source of the metal.

Explanation
Gold does not occur in the combined form because it does not react with air or water. Instead, it is found in its native state, meaning it is naturally found in its pure form without being chemically combined with other elements.

Explanation
The greenish layer that appears on copper vessels is indeed due to the formation of a layer of basic copper carbonate. This occurs when copper reacts with oxygen, moisture, and carbon dioxide in the air. The resulting compound, basic copper carbonate, has a greenish color. Therefore, the assertion and reason are correct and relevant to each other.

Explanation
Froth flotation is a process used for the concentration of sulphide ore. It involves the separation of valuable minerals from gangue by creating a froth on the surface of the ore pulp. In this process, chemicals known as collectors are added to the ore pulp, which selectively attach to the surface of the valuable minerals, making them hydrophobic. Air bubbles are then introduced, which carry the hydrophobic minerals to the surface, forming a froth. The froth is then skimmed off, and the concentrated mineral particles are collected, while the gangue is left behind. This process is commonly used for the concentration of sulphide ores.

Explanation
Coating the surface of iron with a thin layer of zinc is called galvanization. Galvanization is a process where a protective layer of zinc is applied to the surface of iron or steel to prevent it from rusting. The zinc acts as a barrier between the iron and the surrounding environment, preventing the iron from coming into contact with moisture and oxygen, which are the main factors that cause rusting. Galvanization is commonly used in industries such as construction and automotive to protect iron and steel structures from corrosion.

Explanation
The correct answer is Ag - Sn amalgam because silver (Ag) and tin (Sn) are commonly used metals in dental amalgams. Ag - Sn amalgam is known for its good durability, strength, and resistance to corrosion, making it suitable for dental fillings. Copper (Cu) - Sn amalgam is not commonly used in dental fillings, making it an incorrect choice.

Explanation
The reason does satisfy the assertion. Thermite welding involves the use of a mixture of aluminium powder and iron oxide (Fe2O3) as the reactants. The aluminium powder acts as a strong reducing agent, meaning it has the ability to donate electrons and reduce the iron oxide. This reduction reaction leads to the fusion of aluminium and iron, resulting in the formation of molten iron and aluminium oxide. Therefore, the reason that aluminium powder is a strong reducing agent supports the assertion that aluminium powder and Fe2O3 are fused in thermite welding.