Periodicity-trends of the elements on the periodic table Mr. Guerrero LFHS

The 2 reasons for most trends: 1) Effective Nuclear Charge(Zeff)-the ability(pull) of the nucleus to attract its valence electrons. This increases with increasing numbers of protons in the nucleus. The Z eff is explained by Colomb’s Law: Where K = 8.99 x 10 9 N m 2 /C 2 2) Shielding Effect-the interference on effective nuclear charge by core electrons. This effect increases as energy levels increase. Shielding has no effect along a period, only within groups! 1) Effective Nuclear Charge(Zeff)-the ability(pull) of the nucleus to attract its valence electrons. This increases with increasing numbers of protons in the nucleus. The Zeff is explained by Colomb’s Law: 2) Shielding Effect-the interference on effective nuclear charge by core electrons. This effect increases as energy levels increase.

Periodic Trend #1: Atomic Radius- ½ the distance between the nuclei of two identical bonded atoms. Trend Atomic Radius increases toward He.

Ionic Radius-size of cation or anion LEO/GER

Arrange by increasing atomic radius Al, Sr, F, P, Ba K +, K, N 3-, Mg, Mg 2+, Ca 2+, Na, Na +

Why do d-orbitals have n-1 Penetration effect- the effect whereby a valence electron penetrates the core electrons, thus reducing the shielding effect and increasing the pull from the nucleus. (The electron is temporarily closer to the nucleus than normal.) most penetration ns>np>nd>nf least penetration This means that the s electrons “penetrate” or come closer to the core more often than do p, d, or f electrons. Electrons fill orbitals in order of increasing energy. Because of the penetration effect, electrons fill (n+1)s before nd. ((n+1)s has lower energy). For example, 4s fills before 3d.

Electronegativity- the attraction of a nucleus for electrons. Trend: electronegativities increase toward Fluorine Arrange by decreasing electronegativity: Cs, Si, F, Ca, Ga

Electron Affinity (electron loving) Electron Affinity- the energy change associated when an atom, in the gaseous state gains an electron. Electron affinity values are always negative. Rxn: X (g) + e -  X - (g)  E = ???? Trend: same as electronegativity

First Ionization Energy First Ionization Energy – The energy required to remove the first electron from a neutral atom, in the gaseous state. Rxn: X (g)  X + (g) + e -  E = ???? Trend: Valence electrons in smaller atoms are harder to remove, because they are closer to the nucleus. Therefore: He has the highest Ionization energy!

Middle of the p-block exception: Exceptions to the rule Ionization energy and electron affinity have several examples of exceptions. This includes exceptions within the p-block that you are responsible for knowing. Atomic radius and electronegativity do not have as many exceptions, and none are notable enough that you must know.

p-block exceptions: e- affinity & 1 st Ioniz. E.- As e - ’s fill the p-block, the 4 th e- must enter the first occupied orbital. The previous e- causes a large e-/e- repulsion, which causes an anomaly in ionization energy and electron affinity trends.

Ionization energy actually drops between group2-13(Be-B) AND groups 15-16(N-O)

Use arrows to show the increase in: electronegativity atomic radius e- affinity first ionization energy

Second Ionization energy(IE 2 )- the energy required to remove the second electron from a neutral atom, in the gas phase. After the removal of each electron, the electrons get closer to the nucleus, due to less e-/e- repulsion. The energy required to remove the next electron is always greater than the energy required to remove the previous electron. IE 1 < IE 2 <IE 3 < IE 4 ….

H1312 He Li Be B C N O F Ne Na Mg Ionization Energies in kJ/mol

Work out AP released 2007, form B, #6

Polarizability-the distortion of a nonpolar electron cloud to a temporary dipole, by the presence of a near by atom. As the total number of electrons increases, polarizability also increases.