Why atomic size increases down a group

Melting points are varied and do not generally form a distinguishable trend across the periodic table. The metallic character of an element can be defined as how readily an atom can lose an electron. From right to left across a period, metallic character increases because the attraction between valence electron and the nucleus is weaker, enabling an easier loss of electrons.

Metallic character increases as you move down a group because the atomic size is increasing. When the atomic size increases, the outer shells are farther away. The principal quantum number increases and average electron density moves farther from nucleus.

The electrons of the valence shell have less attraction to the nucleus and, as a result, can lose electrons more readily. This causes an increase in metallic character. Another easier way to remember the trend of metallic character is that moving left and down toward the bottom-left corner of the periodic table, metallic character increases toward Groups 1 and 2, or the alkali and alkaline earth metal groups.

Likewise, moving up and to the right to the upper-right corner of the periodic table, metallic character decreases because you are passing by to the right side of the staircase, which indicate the nonmetals. These include the Group 8, the noble gases , and other common gases such as oxygen and nitrogen.

Based on the periodic trends for ionization energy, which element has the highest ionization energy? Answer: C. Helium He Explanation: Helium He has the highest ionization energy because, like other noble gases, helium's valence shell is full.

Therefore, helium is stable and does not readily lose or gain electrons. Answer: A. True Explanation: Atomic radius increases from right to left on the periodic table. Therefore, nitrogen is larger than oxygen. Answer: Lead Pb Explanation: Lead and tin share the same column. Metallic character increases down a column.

Lead is under tin, so lead has more metallic character. Answer: Bromine Br Explanation: In non-metals, melting point increases down a column. Because chlorine and bromine share the same column, bromine possesses the higher melting point. Answer: Sulfur S Explanation: Note that sulfur and selenium share the same column.

Electronegativity increases up a column. This indicates that sulfur is more electronegative than selenium. Answer: Most noble gases have full valence shells. Explanation: Because of their full valence electron shell, the noble gases are extremely stable and do not readily lose or gain electrons. Explanation: The electrons above a closed shell are shielded by the closed shell. S has 6 electrons above a closed shell, so each one feels the pull of 6 protons in the nucleus.

Oxygen O Explanation: Periodic trends indicate that atomic radius increases up a group and from left to right across a period. Therefore, oxygen has a smaller atomic radius sulfur. Answer: B. False Explanation: The reasoning behind this lies in the fact that a metal usually loses an electron in becoming an ion while a non-metal gains an electron.

This results in a smaller ionic radius for the metal ion and a larger ionic radius for the non-metal ion. Electronegativity Trends Electronegativity can be understood as a chemical property describing an atom's ability to attract and bind with electrons. From left to right across a period of elements, electronegativity increases. If the valence shell of an atom is less than half full, it requires less energy to lose an electron than to gain one.

Conversely, if the valence shell is more than half full, it is easier to pull an electron into the valence shell than to donate one. From top to bottom down a group, electronegativity decreases. This is because atomic number increases down a group, and thus there is an increased distance between the valence electrons and nucleus, or a greater atomic radius. Important exceptions of the above rules include the noble gases, lanthanides , and actinides. The noble gases possess a complete valence shell and do not usually attract electrons.

The lanthanides and actinides possess more complicated chemistry that does not generally follow any trends. Therefore, noble gases, lanthanides, and actinides do not have electronegativity values. As for the transition metals, although they have electronegativity values, there is little variance among them across the period and up and down a group. This is because their metallic properties affect their ability to attract electrons as easily as the other elements.

Ionization Energy Trends Ionization energy is the energy required to remove an electron from a neutral atom in its gaseous phase. Trends The ionization energy of the elements within a period generally increases from left to right.

This is due to valence shell stability. The ionization energy of the elements within a group generally decreases from top to bottom. This is due to electron shielding. The noble gases possess very high ionization energies because of their full valence shells as indicated in the graph.

Note that helium has the highest ionization energy of all the elements. Electron Affinity Trends As the name suggests, electron affinity is the ability of an atom to accept an electron. This is because the number of protons increase moving to the right of the row. As the number of protons increase, the nucleus of the atom becomes more positively charged. The increase in positive charge increases the attraction between the nucleus and the electrons of the atom.

Thus, the electrons are held more tightly towards the nucleus, decreasing the radius. It is important to note that elements in the same period all have the same number of electrons shells, so electron shielding will not be a factor.

Atomic size increases as you go down a column because of the addition of another electron shell and electron shielding. Looking to get ready for the ACT? We can help with ACT Prep. This article was written for you by Samantha , one of the tutors with TestPrep Academy.

Login Get started. ACT Science. School Tutoring November 20, No Comments. Begin typing your search term above and press enter to search. Press ESC to cancel. Skip to content Home Physics Why Atomic size increases down a group and decreases across a period? Ben Davis July 15, Why Atomic size increases down a group and decreases across a period? Why do energy levels increase down a group? Why does Zeff increase across a period?

How do you calculate Zeff? Why does electronegativity increase across Period 3? What is the trend in melting points across Period 3? What property decreases across Period 3? What 3 elements have the highest electronegativity? What group has the highest electronegativity? Which is the correct order of melting points of these Period 3 elements?

What causes the largest changes in melting point across Period 2 elements? Why is sulfur more electronegative than chlorine? Is oxygen more electronegative than chlorine? Is chlorine bigger than sulfur?

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