As can be seen in the figures below, the atomic radius increases from top to bottom in a group, and decreases from left to right across a period. What is the order of the elements from smallest to largest atomic radius?Ītomic radii vary in a predictable way across the periodic table. Lithium Which period has the smallest atomic radius? What element in the second period has the largest atomic radius? Non-metallic tendency increases going from left to right across the periodic table. Metallic tendency increases going down a group. Non-metallic character relates to the tendency to accept electrons during chemical reactions. Metallic character refers to the level of reactivity of a metal. (i) Atomic size increases as we move from top to bottom because each time one new shell is added and electrons in the outermost shell move away from the nucleus.ĭoes metallic character decreases down a group? Why does atomic size increase from top to bottom? Down a group, the number of energy levels (n) increases, so there is a greater distance between the nucleus and the outermost orbital. In general, atomic radius decreases across a period and increases down a group. Why does atomic size increase as you go down a grouping in the table? Anions are generally larger than cations. Basically, as we move down the periodic table, the size of the nucleus increases, and concomitantly more electrons are present to “shield” the valence electrons from the charge. Why do both atomic size and ionic size increase as you move down a group?ġ Answer. The electrons are thus attracted to the nucleus more strongly, and the atomic radius is smaller (this attraction is much stronger than the relatively weak repulsion between electrons). As you move from left to right across a period, the number of protons in the nucleus increases. Why do atoms get smaller as you move down a group?Ĥ Answers. The new energy shells provide shielding, allowing the valence electrons to experience only a minimal amount of the protons’ positive charge. Once again protons are added moving down a group, but so are new energy shells of electrons. The atomic radius increases moving down a group. Why does the atomic radius tend to increase as you move down a group but decrease as you move across a period? One proton has a greater effect than one electron thus, electrons are pulled towards the nucleus, resulting in a smaller radius. This is caused by the increase in the number of protons and electrons across a period. Why does atomic size decreases as you go from left to right across a period?Ītomic radius decreases from left to right within a period. Therefore, the size of atoms decreases as one moves across a period from left to right in the periodic table.
Why does atomic size increase down a group and decrease left to right?Įxperiments have shown that the first case is what happens: the increase in nuclear charge overcomes the repulsion between the additional electrons in the valence level.
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