Which atom in each of the following pairs has a larger radius? (a) Na or K (b) V or Ta (c) V or Zn (d) Li or Ba

Key Concepts

Atomic Radius

Atomic radius is defined as the distance from the nucleus of an atom to the outermost shell of electrons. It is a key factor in determining the size of an atom and varies across the periodic table. Generally, atomic radius increases down a group due to the addition of electron shells, while it decreases across a period from left to right due to increased nuclear charge attracting electrons more strongly.

Periodic Trends

Periodic trends refer to the predictable patterns observed in the properties of elements as you move across or down the periodic table. For atomic radius, the trend shows that elements in the same group have larger radii as you move down, while elements in the same period have smaller radii as you move from left to right. Understanding these trends is essential for comparing the sizes of different atoms.

Effective Nuclear Charge

Effective nuclear charge (Z_eff) is the net positive charge experienced by an electron in a multi-electron atom. It accounts for the shielding effect of inner electrons that reduces the full nuclear charge felt by outer electrons. A higher effective nuclear charge leads to a smaller atomic radius, as the increased attraction pulls the outer electrons closer to the nucleus, which is crucial for understanding the size differences in the given pairs.