Periodic Classification Of Elements - Paper I

Explanation
The electronic configuration of the atom of an element X is 2, 8, 4. This means that X has 2 electrons in its first energy level, 8 electrons in its second energy level, and 4 electrons in its third energy level. According to the modern periodic table, elements with similar electronic configurations are placed in the same group. In this case, X has 4 electrons in its outermost energy level, which corresponds to group 14. Therefore, element X is placed in the 14th group of the periodic table.

Explanation
Potassium (K) would lose an electron easily because it is located in Group 1 of the periodic table, which means it has one valence electron. Valence electrons are the outermost electrons in an atom and are involved in chemical reactions. Since potassium only has one valence electron, it is easier for it to lose that electron and achieve a stable electron configuration, resulting in a positive charge.

Explanation
Elements belonging to the same group in the periodic table have similar chemical properties and the same number of valence electrons. In this case, element A has an atomic number of 9 and element C has an atomic number of 17. Both elements belong to Group 7 of the periodic table, also known as the halogens. Therefore, A and C belong to the same group.

Explanation
As we move down a group in the periodic table, the number of shells in the atoms increases, resulting in an increase in atomic radius. The metallic character also increases as we move down the group. However, the number of valence electrons remains constant within a group as the elements have the same outermost electron configuration. Therefore, valence electrons do not increase while moving down the group of the periodic table.

Explanation
The Newlands Law of Octaves was a classification system proposed by John Newlands in 1864, which stated that when elements are arranged in order of increasing atomic weight, every eighth element would have similar properties. However, this law was found to be applicable only up to the element calcium. Beyond calcium, the pattern of properties did not repeat every eighth element, thus making the law invalid for further classification.

Explanation
The element X forms an oxide X2O3. The formula of the oxide indicates that the element has a valency of +3. Group 13 elements in the periodic table have a valency of +3, which means that the element X is placed in group 13.

Explanation
The atomic radius of an element is determined by the number of electron shells and the effective nuclear charge. As we move down a group in the periodic table, the number of electron shells increases, leading to an increase in atomic radius. Among the given elements, K has the largest atomic number and therefore the most electron shells, making it the element with the largest atomic radius.

Explanation
The element with electronic configuration 2, 8 belongs to the noble gases group in the modern periodic table. Noble gases have a completely filled outermost energy level, which makes them very stable and unreactive. Group 18 is known as the noble gases group because it consists of elements with completely filled outermost energy levels. Therefore, the element with electronic configuration 2, 8 would be located in group 18 of the periodic table.

Explanation
The valence shell for the elements of the second period of the modern periodic table is the L shell. The L shell is the outermost shell for these elements and contains the valence electrons, which are the electrons involved in chemical bonding.

Explanation
As you go from left to right across the periods of the periodic table, the correct trend is that the atoms do not lose their electrons more easily. In fact, they tend to gain electrons to achieve a stable electron configuration. This is because as you move across the periodic table, the atomic radius decreases and the effective nuclear charge increases, making it more difficult for the atoms to lose electrons. Therefore, the statement that the atoms lose their electrons more easily is not correct.