Term | Definition |
Groups | Columns |
Periods | Rows |
Aufbau Principle | Group number indicates number of electrons in the valence shell of that element in the main group. |
Vertical Trend | The greater the (n), shell number, the further away it is from the nucleus. |
Horizontal Trend | Across a period the size |
Valence electrons | Outermost electrons of an atom |
Nuclear charge (Z) | The number of protons in the nucleus of an atom |
Effective Nuclear Charge (Z eft) | Actual magnitude of positive charge that is "experienced" by an electron in the atom (Zeff= Z-core electrons) |
Shielding/Screening | When electrons are simultaneously attracted to the nucleus ad repelled by one another |
Core elctrons | Electrons in the completed inner shells |
Atomic radius | The distance between the nucleus of an atom and its valence shell\(increases down a group while it decreases across a period) |
Metallic radius | Half the distance between the nuclei of two adjacent, identical metal atoms |
Covalent radius | Half the distance between adjacent, identical nuclei that are connected by a chemical bond |
Ionization Energy | The minimum energy required to remove an electron from an atom in the gas phase
(Increases across a period while it decreases down a group) |
Ion | Chemical species with a net charge that results from Ionization energies |
Cation | Ion with a net positive charge |
IE down a group | Decreases, The electron is further down away from the nucleus. Therefore, it is less tightly held to the nucleus and less energy is needed to ionize. |
IE across a row | Increases, electron is more tightly held (more protons in the nucleus, and "n" is constant). Therefore, more energy is needed to ionize. |
Electron Affinity | Energy released when an atom in the gas phase accepts an electron. It can be released and absorbed |
The higher the electron affinity | The more energy is released |
Electron Affinity down a group | Decreases, less energy released |
Electron Affinity across a period | Increases, but increase is not smooth |
Nonmetals | Atoms that have larger number of electrons in their valence shell and tend to form negative ions. (Poor conductors of heat and electricity, high electron affinity) |
Metalloids | Have some metallic and nonmetallic properties, "borderline" elements |
Nole Gases | Group 8A elements. High ionization energy and rarely enter into a chemical reaction |
Monatomic Ions | Those consisting of a single atom that has either gained or lost one or more electrons |
Isoelectronic | Species with the same electron configuration |
Ionic radius | The radius of a cation or anion |
Isoelectronic series | A series of two or more species that have identical electron configuration but different nuclear charges |