Test: The Periodic Table - Class 9 MCQ

Inert gases, also known as noble gases, are found in Group 18 of the periodic table. These gases have a complete outer electron shell, making them chemically stable and largely unreactive with other elements.

Transition metals are known for forming colored ions and compounds, which is a result of their ability to lose different numbers of electrons and participate in various oxidation states. This property makes them important in many chemical reactions and applications.

Atomic size increases down a group due to the addition of electron shells, which results in greater distance between the nucleus and the outermost electrons. This increase in distance outweighs the effect of increased nuclear charge, leading to larger atomic radii.

Mendeleev developed the first periodic table by arranging 63 known elements in order of increasing atomic mass and grouped them by similar properties. His periodic law laid the groundwork for later advances in the classification of elements.

Alkali metals are soft and have low melting points compared to many other metals. This softness makes them easy to cut with a knife, and their reactivity increases as you move down the group from lithium to francium.

Alkali metals are found in Group 1 of the periodic table. These elements are characterized by having one valence electron, making them highly reactive and prone to forming strong bases when they react with water.

The modern periodic table is organized by atomic number, which is the number of protons in an atom's nucleus. This arrangement reflects the periodic nature of element properties and provides a more accurate classification than previous methods based on atomic mass.

Chlorine is classified as a halogen and belongs to Group 17 of the periodic table. Halogens are known for their high reactivity and tendency to form diatomic molecules, such as Cl₂, and various compounds with metals.

Dobereiner's triads grouped elements in sets of three based on their atomic mass, where the atomic mass of the middle element was approximately the average of the other two. This method highlighted certain patterns in the properties of elements, although it was later found insufficient for all known elements.

The reactivity of alkali metals increases as you move down the group. This is due to the increasing atomic size and the decreasing ionization energy required to remove the outermost electron, making it easier for these metals to participate in chemical reactions.

Mendeleev left gaps in his periodic table to accommodate elements that had not yet been discovered. He believed that these gaps would eventually be filled by new elements, and he even predicted the properties of some of these undiscovered elements based on the properties of surrounding elements.

Noble gases have complete outer electron shells, which makes them very stable and largely unreactive. This stability is why they are often found in nature as monoatomic gases and do not readily form compounds.

Transition metals are characterized by their ability to exhibit variable valencies, which allows them to form different types of ions and compounds. This property, along with their high melting and boiling points, distinguishes them from other groups of elements.

Henry Moseley discovered that atomic number, rather than atomic mass, is a more fundamental property that defines the arrangement of elements. This insight led to the modern periodic law, which states that the properties of elements are a periodic function of their atomic numbers.

The classification of elements was primarily aimed at organizing the study of elements, which facilitated easier comparison and understanding of their properties. This organization helped scientists discern relationships among elements and their characteristics.

Mendeleev's periodic table did not assign separate places for isotopes, which are atoms of the same element with different atomic masses. This oversight meant that isotopes were grouped with their corresponding element, despite significant differences in their properties.

Elements in the same group of the periodic table generally have the same valency, which is determined by the number of electrons in their outermost shell. This similarity leads to comparable chemical behavior and reactivity among these elements.

Newland's Law of Octaves states that when elements are arranged by increasing atomic mass, every eighth element exhibits similar properties to the first. This arrangement resembled musical octaves, demonstrating periodicity in the properties of elements.

Periodic trends in properties such as atomic size and metallic character are primarily influenced by the nuclear pull (the attraction between protons and electrons) and electron shielding (the effect of inner shell electrons reducing the pull experienced by outer shell electrons). These factors determine how elements behave as you move across periods or down groups.

Carbon is classified as a representative element, which is found in the main group of the periodic table. These elements typically have incomplete outer electron shells and exhibit a wide range of properties, including both metallic and non-metallic characteristics.