An atom or ion with no unpaired electrons is not attracted by a magnet If an

An atom or ion with no unpaired electrons is not

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An atom or ion with no unpaired electrons is not attracted by a magnet. If an orbital is completely filled: It has two electrons, one with an +½ spin and ½ spin. The two electron’s spins cancel out. The net spin is zero.
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The Level of Paramagnetism Can Be Measured with a Gouy Balance
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Learning Check Which of these species is paramagnetic: F , Zn 2+ , and Ti? Answer: Ti
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Most Species are Diamagnetic Stable substances seldom contain free atoms. Instead, atoms are bonded together in molecules, resulting in the pairing of electrons and the cancellation of spin. Paramagnetism is observed primarily among salts of the transition and rare-earth metals, whose cations have partially filled d and f orbitals.
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Excited States A ground-state configuration is the most stable arrangement of electrons, so an atom or ion will usually have this configuration. When an atom absorbs energy, however, it can reach an excited state with a new electron configuration. Ex. Sodium, Na Ground-state configuration: [Ne] 3 s 1 Possible Excited-state configurations: [Ne] 3 p 1 or [Ne] 4 s 1
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Excited State Species Have Many Applications Excited atoms are unstable and spontaneously return to the ground-state configuration, giving up their excess energy in the process. Example Excited Na gives off photons as it returns to ground state in sodium vapor lamps. Excited Sr 2+ ions emit red light in highway flares as they relax to ground state. Excited metals used in fireworks emit light as they return to ground state.
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Underlying Patterns of the Periodic Table Atomic orbitals become larger and less stable as principal quantum number n increases (and Z eff increases slowly. Orbitals expand, stability decreases. n is the most important factor in determining orbital size and stability within a column.
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Underlying Patterns of the Periodic Table Any given atomic orbital becomes smaller and more stable as atomic number Z increases while n is fixed. Orbitals shrink, stability increases.
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Periodic Trends in Atomic Radius The size of an orbital increases: From top to bottom in a column on the periodic table. n increases from top to bottom. From right to left in the periodic table. Z eff decreases from right to left .
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Trends in Atomic Radii Li Na K Cs Rb
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Learning Check For each of the following pairs, predict which atom is larger and why: Si or Cl, S or Se, and Mo or Ag. Answers: Si is larger than Cl. Se is larger than S. Mo and Ag are approximately the same size because of the offsetting effects of screening and Z eff .
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