Periodic Trends

Atomic Radius Atomic Radius Ionic Radius Ionic Radius Oxidation Number Oxidation Number Electronegativity Electronegativity Ionization Energy Ionization Energy Electron Affinity Electron Affinity All of these characteristics can be predicted by the atoms electron configuration All of these characteristics can be predicted by the atoms electron configuration

Atomic Radius the distance from the center of an atom’s nucleus to the outermost electron the distance from the center of an atom’s nucleus to the outermost electron Measured using two atoms, why? Measured using two atoms, why? Distance between distance halfway between two adjacent nuclei in a covalent bond. Distance between distance halfway between two adjacent nuclei in a covalent bond.

As we saw in our graphing activity and the previous diagrams the atomic radius… As we saw in our graphing activity and the previous diagrams the atomic radius… Decreases going across a period Decreases going across a period Increases going down a group Increases going down a group But why??? But why???

Take a look at the electron configurations Take a look at the electron configurations When you go across a period what happens? When you go across a period what happens? Your not increasing your E-level, however your increasing your neg. charge Your not increasing your E-level, however your increasing your neg. charge 4 e-e- e-e- e-e- e-e- 8 e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e-

As you increase the neg. charge the attraction between the E-level and the nucleus increases, pulling the E-level in closer decreasing the atomic radius As you increase the neg. charge the attraction between the E-level and the nucleus increases, pulling the E-level in closer decreasing the atomic radius

As you move down a group another principal E-level (shell) is added in each row, making atoms larger. As you move down a group another principal E-level (shell) is added in each row, making atoms larger. n=1 n=2 n=3 n=5 n=4

Ionic Radius Dogion, Cation, Union, Onion, Anion, Lion Dogion, Cation, Union, Onion, Anion, Lion Cation – Pos. Charged Ion Cation – Pos. Charged Ion Anion – Neg. Charged Ion Anion – Neg. Charged Ion How does the formation of an ion affect the radius, now call the IONIC RADIUS? How does the formation of an ion affect the radius, now call the IONIC RADIUS?

Radii of ions compared to atoms Cations: (+) Cations: (+) become smaller: 1. Reduced the number of energy levels. 2. Positive charged nucleus attracting fewer e-. EX: Anions: (-) Anions: (-) become larger: 1. The number of electrons is greater than the nuclear charge (e - held more loosely). 2. Electrons repel. Na Na + Cl Cl - Metals Nonmetals

Trends in Ionic Radius

Oxidation Number Pos. or neg. charges on ions that tell how many electrons have been gained or lost Pos. or neg. charges on ions that tell how many electrons have been gained or lost Our knowledge of e - configurations and the stability of noble gases allows us to predict oxidation numbers for elements. Our knowledge of e - configurations and the stability of noble gases allows us to predict oxidation numbers for elements.

Oxidation Numbers by Group Tend to have more than one oxidation number (+1 to +7) 3+ varies or 4+

Ionization Energy Energy required to remove an electron from an atom (form a cation) Energy required to remove an electron from an atom (form a cation) Measured in kJ/mol Measured in kJ/mol 11 e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- 17 e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- 1 e - 7 e - Which RED electron would be easier to remove? NaCl

As you move across a period the I.E. ____? As you move across a period the I.E. ____? INCREASES INCREASES As you move down a family the I.E. ______? As you move down a family the I.E. ______? DECREASES DECREASES Your turn…Explain why this happens. Use your knowdlege of atomic radius. Your turn…Explain why this happens. Use your knowdlege of atomic radius.

Ionization energy increases diagonally from bottom left corner to top right corner. Which element has the highest I.E.?

Multiple Ionization Energies Additional e - can be lost from an atom and the ionization energies can be measured. Additional e - can be lost from an atom and the ionization energies can be measured. IONIZATION ENERGIES (kilojoules per mole) Element1 st 2 nd 3 rd 4 th 5 th H He Li Be B

Electronegativity Ability of an atom to attract an electron Ability of an atom to attract an electron Follows the same general trend as I.E. Follows the same general trend as I.E. Remember that all atoms WANT to be STABLE!! Remember that all atoms WANT to be STABLE!! (obtain an complete outer shell) (obtain an complete outer shell) The closer they are to completing that shell the higher the EN The closer they are to completing that shell the higher the EN

Electronegativity Values Which element has the highest EN?

Electron Affinity The energy change that occurs when an atom gains an extra electron The energy change that occurs when an atom gains an extra electron Expressed in kJ/mol Expressed in kJ/mol Mostly neg. values, some pos. values Mostly neg. values, some pos. values What do the neg. and pos. values mean?? What do the neg. and pos. values mean??

Neg. = energy is released during rxn. Neg. = energy is released during rxn. F (g) + e - F - (g) + Energy F (g) + e - F - (g) + Energy Pos. = energy is needed to power rxn. Pos. = energy is needed to power rxn. Mg (g) + e - + Energy Mg - (g) Mg (g) + e - + Energy Mg - (g) Mg wants to be a cation is energy is required to make it an anion Mg wants to be a cation is energy is required to make it an anion