Chemistry Midterm Exam Notes SCH3U7 Periodic Trends & Periodic Spectrums Atomic Radius — the distance from the centre of an atom to its outermost electron orbital ( increases going left , and going down ) — measured in Angstroms ( * 10 -10 m) — the valence electrons have a portion of the nuclear charge shielded by the inner electron energy levels ( shielding effect ) Net Charge — the total positive charge of the nucleus remaining after the shielding of the inner energy levels (which cancels out a portion of the charge) NOTE : F = (K * Q 1 * Q 2 ) / D 2 ● F = Force of Attraction (FoA) ● Q 1 & Q 2 = charge ● K = specified constant ● D = distance between charges Ionization Energy — the amount of energy required to remove the outermost electron (measured in KJ / mol ) ( increases going right , and going up ) — closer to nucleus means it has a stronger FoA and IE — decreases going down since electron is further from the nucleus — increases going right since it has a higher net charge (causing an increase in FoA ) — filled and half-filled sublevels have more stability (which means it has a higher FoA ) Electron Affinity — the amount of energy released when an electron is added to the atom ( increases going right , and going up ) — decreases going down since there is a lower FoA to the electrons — increases going right since there is a higher net charge (causing an increase in the FoA ) — filled and half-filled sublevels require energy as they
would need to create the extra room for the electron Electronegativity — relative scale showing the ability of an atom to attract a shared pair of electrons ( increases going right , and going up ) — decreases going down since there are additional energy levels (which decreases the FoA ) — increases going right since the atom is closer to completing the desired octet Continuous Spectrum — spectra in which all frequencies are present Emission Spectrum — when energy is applied to a gas sample , causing the electrons to become excited and release energy (which is shown as coloured lines on a black background ) Absorption Spectrum — when a continuous spectra is passed through a gas sample , which absorbs the energy (shown as black lines on a coloured background ) VSEPR Theory Bonded atoms Lone Pairs 3-D Shape VSEPR Name Bond Angles Example 2 0 Linear 180 BeCl 2 3 0 Trigonal Planar 120 BF 3 2 1 Bent < 120 SO 2
4 0 Tetrahedral 109.5 CH 4 3 1 Trigonal Pyramidal < 109.5 NH 3 2 2 Bent < 109.5 H 2 0 5 0 Trigonal Bipyramidal 90, 120 PCl 5 4 1 See-Saw 90, < 120 SF 4 3 2 T- Shaped 90 ClF 3 2 3 Linear 180 XeF 2 6 0 Octahedral 90 SF 6
5 1 Square Based Pyramid 90 BrF 5 4 2 Square Based Planar 90 XeF 4 Chemical Reactions Synthesis — metallic oxide + water ➡ base — non-metallic oxide + water ➡ acid — metallic oxide + non-metallic oxide ➡ salt Decomposition — base ➡ metallic oxide + water — acid ➡ non-metallic oxide + water — salt ➡ non-metallic oxide + metallic oxide Combustion — fuel [C_H_O_] + O 2 ➡ CO 2 + H 2 O + Energy [E] — fuel [C_H_O_] + O 2 ➡ CO + . . + Energy [E] Single Displacement — A + BC ➡ AC + B —
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