Chemistry Chapter 3 Notes I Valence Electrons A Core Electrons 1 Sublevels that are full are generally very stable and closer to the nucleus a This means that electrons can neither be added or removed 2 Only the outmost s sublevel can give up electrons when it is filled because it is really high in energy a Also only has 2 electrons 3 Electrons in filled sublevels other than s are called core electrons B Valence Electrons 1 High energy electrons used in chemical bonding 2 3 4 a Found in the outer s sublevel and partially filled sublevels Occupy the valence orbitals a Can be shared with other atoms to produce bonds Given as the Valence Electron Configuration a Electron configurations vary periodically part of why chemical properties are periodic in the table to begin with Valence Orbitals are used to accept electrons from other atoms C Configurations 1 Electrons in filled d sublevels aren t valence electrons II Shielding and Effective Nuclear Charge A Shielding 1 Valence electrons aren t exposed to the full positive nuclear charge because they re shielded by the core electrons 2 The nuclear charge that is actually experiences by a valence electron is called the Effective Nuclear Charge a Equal to Charge of the nucleus Z portion sheilded by other electrons B Effective Nuclear Charge 1 Z increases as protons are added but increases more slowly because extra valence electrons don t sheild a Zeff is low for metals and high for nonmetal 2 Each nodal plane in an orbital reduces electron density at the nucleus 3 Shielding ability of electrons in a level decreases as their l number increases a Sheilding ability of electrons goes s p d f III Relative Sizes of Atoms A Relative Atomic Size 1 Size of atoms depends on two factors a N quantum number avaerage distance between an electron nucleus Constant within a period changes down a group b Zeff increases going across a period IV V VI VII Orbital Energy Ionization Energy Electronegativity Magnetic Properties