© Copyright Pearson Prentice Hall Slide 1 of 31 Periodic Trends > Types of Periodic Trends 4 Periodic Trends 1.Atomic Radii (AR) 2.Ionization Energy (IE) 3.Ionic Radii (IR) 4.Electronegativity (EN)

Slide 2 of 31 © Copyright Pearson Prentice Hall Periodic Trends > Trends in Atomic Size The atomic radius is one half of the distance between the nuclei of two atoms of the same element when the atoms are joined. 6.3

Slide 3 of 31 © Copyright Pearson Prentice Hall Periodic Trends > Trends in Atomic Size 6.3

Slide 4 of 31 © Copyright Pearson Prentice Hall Periodic Trends > Trends in Atomic Size 6.3

Slide 5 of 31 © Copyright Pearson Prentice Hall Periodic Trends > Atomic Radii (AR) Periodic Trend Down a Group: Trend: The atomic radius increases as the atomic # increases within a group Reason: The number of protons in the nucleus (NUCLEAR CHARGE) increases, increasing the positive charge drawing electrons close to the nucleus, but the number of occupied orbitals also increases the SHIELDING of electrons from the effect of the nuclear charge. (SHIELDING EFFECT)

Slide 6 of 31 © Copyright Pearson Prentice Hall Periodic Trends > Across a Period: Trend: Atomic size decreases across a period from left to right. Reason: Electrons are added to the same energy level so shielding is constant for all elements in a period. The increasing nuclear charge pulls the electrons in closer to the nucleus.

Slide 7 of 31 © Copyright Pearson Prentice Hall Periodic Trends > Ions An ion is an atom or group of atoms that has a positive or negative charge. A cation is an ion with a positive charge. An anion is an ion with a negative charge. 6.3

© Copyright Pearson Prentice Hall Slide 8 of 31 Periodic Trends > Ions Metals elements lose valence electrons to form cation ions. Cation radii (IR) are always smaller than atomic radii (AR) [i.e. IR < AR] 6.3

© Copyright Pearson Prentice Hall Slide 9 of 31 Periodic Trends > Ions Non-metal elements gain valence electrons to form anion ions. Anion radii (IR) are always larger than atomic radii (AR) [i.e. IR > AR] 6.3

Slide 10 of 31 © Copyright Pearson Prentice Hall Periodic Trends > Trends in Ionic Size Relative Sizes of Some Atoms and Ions 6.3

© Copyright Pearson Prentice Hall Slide 11 of 31 Periodic Trends > Trends in Ionic Size 6.3 Size generally increases

© Copyright Pearson Prentice Hall Slide 12 of 31 Periodic Trends > Ionic Radii Periodic Trend Periodic Trend for Ionic Radii (IR) Down a Group: Trend: Size of the Ion generally increases. Reason: Atomic Number increases. Number of energy levels increases.

© Copyright Pearson Prentice Hall Slide 13 of 31 Periodic Trends > Across a Period: Metals large  small, then Non-metal large  small (Caution: Are not looking at same charge ion when across period) Metals: IR vs. AR :Ionic radii is smaller than atomic radii. Cation size decreases. Reason: When an atom loses an electron, the attraction between the remaining electrons and the nucleus increases and electrons are drawn closer to the nucleus. Also, metals tend to lose their outermost electrons- one fewer occupied energy level. Non-metals: IR vs. AR : The trend is opposite Ionic radii is larger than atomic radii. Anion size decreases Reason: The total number of electrons will be the same but the nuclear charge increases so the attraction from the protons increases, decreasing overall size.

Slide 14 of 31 © Copyright Pearson Prentice Hall Periodic Trends > Trends in Ionization Energy Ionization Energy (IE) - The energy required to remove the first valence electron from an atom (atom is in the gas phase). What is holding the valence electron to the atom? Valence electron tightly held or loosely? 6.3

Slide 15 of 31 © Copyright Pearson Prentice Hall Periodic Trends > Trends in Ionization Energy 6.3

Slide 16 of 31 © Copyright Pearson Prentice Hall Periodic Trends > Trends in Ionization Energy 6.3

© Copyright Pearson Prentice Hall Slide 17 of 31 Periodic Trends > Trends in Ionization Energy 6.3

© Copyright Pearson Prentice Hall Slide 18 of 31 Periodic Trends > Ionization Energy (IE) Periodic Trend Periodic Trend for Ionization Energy (IE) Down a Group: Trend: Decreases as atomic # increases. Reason: Nuclear charge has a decreasing effect on electrons as they move further and further away from the nucleus. Shielding effect is greater as you move down a group. Across a Period: Trend: Increases from left to right. Reason: The nuclear charge increases, the shielding effect remains the same, electrons are more attracted to the nucleus as you move across the period.

© Copyright Pearson Prentice Hall Slide 19 of 31 Periodic Trends > Ionization Energy (IE) Periodic Trends Two Exception to 1 st Ionization Energy (IE) (Across the Period): 1. Be  B Trend: Drop in energy required. Reason: Easier to take a “p” than an “s” electron because it is further away from the nucleus. 2. N  O Trend: Drop in energy required. Reason: p4 electron is the first pair in the p sublevel. Repulsion created, lowers the amount of energy required to remove the electron.

Slide 20 of 31 © Copyright Pearson Prentice Hall Periodic Trends > Trends in Electronegativity Electronegativity is the ability of an atom, in a chemical bond, to attract the shared valence electrons to itself. (i.e. the shared valence electrons are physically closer to the higher EN value atom than the other atom in the chemical bond). 6.3

Slide 21 of 31 © Copyright Pearson Prentice Hall Periodic Trends > Trends in Electronegativity In general, electronegativity values decrease from top to bottom within a group. For representative elements, the values tend to increase from left to right across a period. 6.3

Slide 22 of 31 © Copyright Pearson Prentice Hall Periodic Trends > Trends in Electronegativity Representative Elements in Groups 1A through 7A 6.3

Slide 23 of 31 © Copyright Pearson Prentice Hall Periodic Trends > Summary of Trends 6.3 Atomic Size Increases Decreases Size of cationsShieldingNuclear ChargeElectronegativityIonization energySize of anionsIonic size Constant