Periodic Trends The periodic table has trends where
Periodic Trends The periodic table has trends where predictions can be made about elements
Atomic Radius For metals, this is ½ the distance between adjacent nuclei in a crystal of the element. For other elements it is half the distance between nuclei of identical atoms that are bonded together.
Atomic Radius Trends within periods – generally decrease from left to right because of increasing positive charge in the nucleus. No shielding for electrons
Atomic Radius Trends within groups – generally increases as you go down a group. Atom is getting larger and adding e- to inner shells, which shields outer e- from increased nuclear pull
Atomic Radius
Atomic Radii
Ionic Radius An ion is an atom that has gained or lost one or more electrons and takes on either a positive or negative charge. ½ the distance between the adjacent nuclei in either a crystal of the element or two identically bonded elements is the ionic radius
Ionic Radius Period trends – for positive ions, generally decreases as you move left to right, then the much larger negative ions begins and they, too decrease in size from left to right. Group trends – increase size as you go down a group
Ionic Radius
Ionization Energy required to remove an electron from a gaseous atom. In other words, how strongly does an atom hold onto its valence electrons?
Ionization Energy Period Trends – generally increase across a period Group Trends – generally decrease down a group ( increased size makes it easier to pull off an electron)
Ionization Energy
Ionization Energy
Ionization Energy The value for pulling off the 1 st e- is called “ 1 st ionization energy. ” It is possible to pull off more than one e. When pulling off the 2 nd e- it is called “ 2 nd ionization energy” and so on.
Electronegativity Relative ability of an element to attract electrons in a chemical bond Period trends – generally increases as you move left to right across the period. Highest electronegativities are found in the upper right of the table. Group trends – generally decrease as you go down a group. Lowest electronegativities are found on the lower left of the table.
Electronegativity
Electronegativity
Electron Affinity Neutral atoms can also acquire electrons Electron affinity=energy change that occurs when an electron is acquired by a neutral atom Most release energy when this happens, but others must be “forced” to “take” the electron & energy is added.
Electron Affinity Period trends – generally increase (become more negative) across the period Group trends – are irregular, but generally decrease down a group (get less negative)
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