Q1: Referring to the periodic table of elements, it is found that with increasing atomic number. The atomic size in the same

ANS:D - both 'b' & 'c'.

Referring to the periodic table of elements, with increasing atomic number: The atomic size in the same period decreases. The atomic size in the same group increases. So, the correct answer is both 'b' & 'c'.

1. Period: A period in the periodic table refers to a horizontal row of elements. As you move from left to right across a period, the atomic number (number of protons) increases. In general, within the same period, the atomic size decreases. This is because, as you move across a period, the number of protons in the nucleus increases, resulting in a greater positive charge in the nucleus. This increased positive charge pulls the outermost electrons closer to the nucleus, resulting in a decrease in atomic size. Electrons are added to the same valence shell as you move across a period, but the increasing nuclear charge outweighs the shielding effect of additional electrons, leading to a decrease in atomic size.
2. Group: A group in the periodic table refers to a vertical column of elements. Elements within the same group have similar chemical properties because they have the same number of valence electrons. As you move down a group, the atomic number increases, but the atomic size increases as well. This is because the number of electron shells (energy levels) increases with each row down the group. The additional electron shells further from the nucleus result in increased shielding of the outer electrons from the positive charge of the nucleus. Additionally, the increase in the number of electron shells means that there are more electrons present, leading to greater electron-electron repulsion, which causes the outermost electron cloud to expand further from the nucleus. Consequently, the atomic size increases as you move down a group in the periodic table.