Periodic Trends Chapter 6 Section 3

Atomic radius Electron clouds do not have clearly defined edges. Electron clouds do not have clearly defined edges. Atomic size is defined by how closely an atom lies to a neighboring atom. Atomic size is defined by how closely an atom lies to a neighboring atom.

Trends within periods In general, there is a decrease in atomic radii as you move left-to-right across a period. In general, there is a decrease in atomic radii as you move left-to-right across a period. It’s caused by an increasing positive charge in the nucleus and the fact that the principal energy level within a period remains the same. It’s caused by an increasing positive charge in the nucleus and the fact that the principal energy level within a period remains the same. Increased nuclear charge pulls outermost e - closer. Increased nuclear charge pulls outermost e - closer.

Trends within groups Atomic radii generally increase as you move down a group. Atomic radii generally increase as you move down a group. The nuclear charge increases and e - are added to successively higher principal energy levels. The nuclear charge increases and e - are added to successively higher principal energy levels. Inner e - orbitals shield outer e -. Inner e - orbitals shield outer e -.

Ionic Radius An ion is an atom or a bonded group of atoms that ha a positive or negative charge. An ion is an atom or a bonded group of atoms that ha a positive or negative charge. When atoms lose e- and form positively charged ions, they always become smaller. When atoms lose e- and form positively charged ions, they always become smaller. NaNa + NaNa +

Ionic Radius (cont.) When atoms gain e- and form negatively charged ions, they always become larger. When atoms gain e- and form negatively charged ions, they always become larger. SS 2- SS 2-

Trends within periods and groups Elements on the left side form cations and elements on the right form anions. Elements on the left side form cations and elements on the right form anions. As you move from left-to-right, the ionic radius decreases. As you move from left-to-right, the ionic radius decreases. As you move down a group, there is a gradual increase in ionic size. As you move down a group, there is a gradual increase in ionic size.

Ionization Energy Ionization energy is defined as the energy required to remove an e - from a gaseous atom. Ionization energy is defined as the energy required to remove an e - from a gaseous atom. The loss of an electron results in an ion. The loss of an electron results in an ion. It’s an indication of how strongly an atom’s nucleus holds onto its valence e -. It’s an indication of how strongly an atom’s nucleus holds onto its valence e -.

Ionization Energy (cont.) After removing the 1 st e-, it is possible to remove additional e-. (First ionization energy) After removing the 1 st e-, it is possible to remove additional e-. (First ionization energy)

Trends within periods First ionization energies generally increase as you move from left-to-right across a period. First ionization energies generally increase as you move from left-to-right across a period. Increased nuclear charge has an increased hold on valence e-. Increased nuclear charge has an increased hold on valence e-. Related to atomic radius decrease. Related to atomic radius decrease.

Trends within groups First ionization energies generally decrease as you move down a group. First ionization energies generally decrease as you move down a group. Valence e- are farther from the nucleus because atomic radius increases. Valence e- are farther from the nucleus because atomic radius increases. The octet rule states that atoms tend to gain, lose or share e- in order to acquire a full set of eight valence e-. The octet rule states that atoms tend to gain, lose or share e- in order to acquire a full set of eight valence e-.

Electronegativity The electronegativity of an element indicates the relative ability of its atoms to attract e- in a chemical bond. The electronegativity of an element indicates the relative ability of its atoms to attract e- in a chemical bond. F is the most electronegative element. F is the most electronegative element. Electronegativity generally decreases as you move down a group and increases as you move left-to-right across a period. Electronegativity generally decreases as you move down a group and increases as you move left-to-right across a period.