Atomic radius, the half of the distance from center to center of two like atoms, increases as you go from top to bottom in groups but decreases as you move from left to right each period. Atomic radius increases within a group because in each group from top to bottom, the number of occupied orbitals between the electrons and the outermost energy level increases, and the added electrons causes the attraction between the electrons and nucleus to decrease. Atomic radius decreases within a period because from left to right, the number of protons and electrons in each atom increases and the attraction between the nucleus and electrons increase, which causes to make the atomic radii decrease. Shielding effect increases within a group and stays constant across periods.
Ionization energy, the energy used to remove electrons from an atom, decreases when going from top to bottom in a group but increases across a period left to right. Electron affinity, the energy change that accompanies the addition of an electron to an atom in the gas phase, decreases within a group but increases across a period. This can be explained by the changes in nuclear charge, atomic radius, and shielding effect.
Elements whose atomic number is over 92, Uranium's, are synthetic. Elements number 93-100 were created by a method of bombarding nuclei with various small particles (protons, electrons, alpha + beta particles, etc.), where the particles would go through nuclear reactions with the targeted nuclei. The particles must be moving very fast and have a lot of energy for them to go through these nuclear reactions. Elements 101+ are made by a different process, where accelerators hurl nuclei at another. Nobelium, 102, was created by crashing Carbon and Curium nuclei together. On August 29, 1982, element 109, Une, was created and identified, although it only lasted 0.0034 seconds.
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Topic 2: Atomic Structure
Topic 4: Ionic and Covalent Compounds
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