Chapter Four Periodic Trends of the Elements

Section 4.1 Development of the Periodic Table

Development of the Periodic Table

Section 4.2 The Modern Periodic Table

Groups of the Periodic Table Main group elements (1,2,13-17) Transition Metals (3-12) Noble Gases (18) Lanthanides and Actinides Elements in same GROUP exhibit similar chemical properties (due to their same number of valence electrons)

Groups of the Periodic Table

Section 4.3 Effective Nuclear Charge

Effective Nuclear Charge Nuclear Charge (Z) is # of protons in the nucleus of an atom (atomic #) Effective Nuclear Charge (Zeff) is the actual magnitude of positive charge “experienced” by an electron

Shielding Effect A simultaneous phenomenon in which electrons are attracted to the positive nucleus while also repelled by other electrons Electrons “shield” other electrons from the positive nucleus

Effective Nuclear Charge Trend Increases steadily as you move across a period Increases as you move down a group (but not as significant as when you move across a period)

Section 4.4 Periodic Trends

Atomic Radius

Atomic Radius

Atomic Radius

Group Quiz #1 For each pairing below, state which atom would have the larger atomic radius Na or K F or O Xe or Kr

Ionization Energy Minimum energy required to remove an electron from an element in the gas phase Creation of a cation (positive ion) First Ionization Energy (Easiest) Second Ionization Energy (Hardest) Etc

Ionization Energy

Electron Affinity Energy RELEASED when an atom in the gas phase ACCEPTS an electron Creation of an anion (negative ion) Same general trend as ionization energy Increases across a period (due to higher Zeff) Decreases down a group (due to shielding)

Electron Affinity

Metallic Character Increases from top to bottom and increases from right to left

Section 4.5 Electron Configuration of Ions

Electron Configuration of Ions Elements want to be just like Noble Gases (very stable elements) Full outer shells (8 v.e. or 2. v.e. w/ Helium) They will lose or gain electrons to do this Let’s look at Na and Cl

Electron Configuration of Ions Write the electron configurations for the following ions: Cr2+ Ti3+ Fe3+

Group Quiz #2 Write the electron configuration for the following ion: Ag+ S2-

Section 4.6 Ionic Radius

Ionic Radius When atoms lose electrons (become cations), radius decreases because of reduction in electron repulsions (and shielding)

Ionic Radius When atoms gain electrons (become anions), radius increases because of the increased electron repulsion (spreads out)

Ionic Radius

Isoelectronic Series Elements that are in an isoelectronic series all have the same electron configuration, but NOT the same size Ex: Ca2+, K+, Ar, Cl-, S2-,P3-

Group Quiz #3 Name 2 elements you would expect to have similar properties to Sr Arrange Ca, Sr, and Ba in order of increasing Ionization Energy For each of the following pairs of elements, indicate which will have the greater electron affinity: Rb or Sr, C or N, O or F? Identify the largest and smallest ion from the following: Mg2+, N3-, O2-, Na+, C4-