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F. Schifano , Department of Science Bayonne High School Bayonne, NJ. Trends in the Periodic Table. Key Skills. Atomic Radius. The “ size ” of the atom Measured as half the distance from the nucleus of one atom to the nucleus of the next Border of the electron cloud is fuzzy
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F. Schifano, Department of Science Bayonne High School Bayonne, NJ Trends in the Periodic Table
Atomic Radius • The “size” of the atom • Measured as half the distance from the nucleus of one atom to the nucleus of the next • Border of the electron cloud is fuzzy • Different atoms have different radii.
Anions • An atom can gain one or more electrons, forming a negatively charged anion. • Anions are larger than their neutral atoms.
Cations • Atoms can give up one or more electrons to form postively charged cations. • Cations are much smaller than their neutral atoms.
Ionic Radius • Cations (+) • Anions (-)
Valence Runs the Show • What charge an atom will acquire when it becomes an ion is easily predicted using the atom’s valence.
What ion is formed by each of the following? • Ba • Ca • Cl • O • Al
Which is larger? • Ba or Ba2+ • Ca or Ca2+ • Cl or Cl- • O or O2- • Al or Al3+
Ionization Energy— Breaking the “Binding Chain” • Ionization energy is the amount of energy in joules it takes to strip an electron off a neutral atom.
Electron Affinity– The “Joy” of Receiving a Gift • Electron affinity is how much energy in joules is released when an atom gains an electron. • The number is given as a negative to show that energy is released from the atom.
Both Ionization Properties Increase Up, Right • Elements with low valence numbers naturally lose electrons when they bond. Their electron affinities and ionization energies are both close to zero. • They don’t fight losing electrons and they don’t take much joy in gaining electrons.
Both Ionization Properties Increase Up, Right • Elements with high valence numbers naturally gain electrons when they bond. Their ionization energies are both far from zero. • They viciously defend their electrons, and celebrate mightily when they get more.