Periodic Table And Periodicity Of Properties

Explanation
The periodic table consists of seven periods, which are horizontal rows. Each period represents the energy levels or shells in which the elements' electrons are arranged. Therefore, the correct answer is 7.

Explanation
The correct answer is IIA. The alkaline earth metals are a group of elements in the periodic table that include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). These elements are found in Group IIA of the periodic table and have similar chemical properties, including having two valence electrons and being relatively reactive.

Explanation
Xe belongs to VIIIA because it is a noble gas. Noble gases are located in Group 18 (VIIIA) of the periodic table and have a full outer electron shell, making them stable and unreactive. Xe, also known as xenon, has a full outer electron shell with 8 valence electrons, which is why it is classified as a noble gas and belongs to VIIIA.

Explanation
Main group elements are arranged in group 8. This is because the main group elements, also known as representative elements, are the elements in the s and p blocks of the periodic table. These elements have valence electrons in the s and p orbitals. Group 8 of the periodic table is known as the noble gases or inert gases. These elements have completely filled s and p orbitals, making them stable and unreactive. Therefore, the main group elements are arranged in group 8.

Explanation
The period number of an element is determined by the highest energy level (shell) that contains electrons in that element's electron configuration. Aluminum (Al) has an atomic number of 13, which means it has 13 electrons. The electron configuration of Al is 1s2 2s2 2p6 3s2 3p1. The highest energy level that contains electrons in Al is the third energy level (shell), so the period number of Al is 3.

Explanation
The valence shell electronic configuration of an element M with atomic number 14 is 3s2, 3p2. This means that in the third energy level, there are 2 electrons in the s subshell and 2 electrons in the p subshell. The valence shell is the outermost shell of an atom, and the electrons in the valence shell are involved in chemical bonding and determining the element's chemical properties.

Explanation
The shielding effect refers to the ability of inner electrons to shield the outer electrons from the positive charge of the nucleus. As we move down a group in the periodic table, the number of energy levels or shells increases. Therefore, Rb, being located at the bottom of the group, is expected to have a greater shielding effect compared to Li, Na, and K, which are located higher up the group.

Explanation
As you move from left to right across a period, the shielding effect does not increase. The shielding effect refers to the ability of inner electrons to shield the outer electrons from the full attraction of the nucleus. As you move across a period, the number of protons in the nucleus increases, leading to a greater nuclear charge. However, the number of inner electrons remains the same, resulting in a constant shielding effect. Therefore, the shielding effect does not increase as you move from left to right across a period.

Explanation
The correct answer is "Relatively high ionization energy." The elements in group IIA (alkaline earth metals) have a higher ionization energy compared to alkali metals because they have a greater number of valence electrons and a stronger attraction between the nucleus and the valence electrons. This makes it more difficult to remove an electron from an atom of an alkaline earth metal, resulting in higher ionization energy.