Presentation on theme: "By: Kyle Chin, Justin Wallace, Jeff Pearson, and Andy Mack"— Presentation transcript:
1 By: Kyle Chin, Justin Wallace, Jeff Pearson, and Andy Mack Atomic Radii Ion SizeBy: Kyle Chin, Justin Wallace, Jeff Pearson, and Andy Mack
2 Definition of Atomic Radii -the distance from the atomic nucleus to the outermost stable electron shell in a neutrally charged atom -one half the distance between nuclei of atoms of the same element that are covalently bonded -measured in picometers (pm)
3 Group Trend for Atomic Radii -As you move down a column, the atomic radius increases-Moving down a group, shells of electrons are added to the nucleus-Each successive shell shields the more distant shells from the nucleus and the valence electrons get farther away from the nucleus-Protons are also added to the atom but the shielding effect of the negatively charged electrons cancel out the added positive charge
4 Period Trend for Atomic Radii -As you move from left to right across a period, the atomic radius decreases-Protons are added to the nucleus of atoms which strongly attract the valence electrons- Electrons in the same shell don’t shield one another from the nucleus effectively so the shells contract, decreasing the overall size of the atom
5 Exceptions for Atomic Radii -In the transition metals, the atomic radii initially decrease for the first few elements, then change very little in the middle elements, but at the end of the series there is a small increase in atomic radii-The small increase in atomic radii is because of the d subshell is filled with electrons and thus the electron-electron repulsions cause the size to increase-Exceptions also exist in the lanthanide and actinide series because of how the f subshells are uniquely filled by electrons
7 Definition of Ion Size-the distance from the atomic nucleus to the outermost stable electron shell in an ion-Ions can either be negatively charged anions or positively charged cations-measured in picometers (pm)
8 Cations-Cations, positively charged atoms, have atomic radii that are always smaller than the neutral atom it was derived from.-When electrons are removed from an atom, the outer shell is lost and the electron-electron repulsions are reduced, allowing all the remaining valence electrons to move closer to the nucleus
9 Anions-Anions, negatively charged atoms, have atomic radii that are always larger than the neutral atom it was derived from.-When an electron is added to an atom, electron-electron repulsions increase dramatically, forcing the valence electrons to move farther apart, increasing the radii.
10 Trends for Ion Size-Periodic trends in the sizes of ions are the same as the atomic radii of neutral atoms, they increase as you progress down a group and decrease as you move across a period.