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Chapter 7

Chapter 7. Periodic Properties of the Elements. Atomic Size. The atomic size of an atom, also called the atomic radius, refers to the distance between an atom's nucleus and its outermost shell.

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Chapter 7

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  1. Chapter 7 Periodic Properties of the Elements

  2. Atomic Size The atomic size of an atom, also called the atomic radius, refers to the distance between an atom's nucleus and its outermost shell. The bonding atomic radius is defined as one-half of the distance between covalently bonded nuclei.

  3. Trends in Atomic Radii increase • In each column(group), atomic radius tends to increase from top to bottom • The rows in the periodic table correlates the energy level. • Outer electrons are farther from the nucleus • Within each row (period), atomic radius tend to decrease from left to right (or increase from right to left) • increase in effective nuclear charge from left to right in a row increase

  4. Ionization Energy • The minimum energy required to remove an electron from the ground state of an isolated gaseous atom or ion. Na(g)  Na+(g) + e- • Endothermic process • Trend is opposite of atomic size • 1st ionization energy increases from left to right across the period due to increase in nuclear charge • 1st ionization energy decreases as you go down a column (or increase as you go up) in a group due to increase in number of shells increase increase

  5. Ionization Energy • It requires more energy to remove each successive electron. • shrinkage in size due to having more protons than electrons • When all valence electrons have been removed, the ionization energy takes a quantum leap. • I1 for Na = 495 kJ/mol and I2 for Na = 4562 kJ/mol • outer electrons closer to the nucleus, therefore harder to remove

  6. Practice: Ionization Energy 1. Problem: Which element has the highest ionization energy of the three? a) Mg, Si, S _____ b) F, Cl, Br _____ 2. Of the following elements, which has the largest first ionization energy? a) B b) N c) P d) Si e) C

  7. Electron Affinity • Electron affinity is the energy change accompanying the addition of an electron to a gaseous atom: F(g) + e− F−(g) • Exothermic (-) process • Periodic trend is same as ionization energy • In every period the element with the highest EA is the halogen.

  8. Trends in Metallic Character • Trend is the same as the atomic size. • Increases from left to right across a period • Increase from top to bottom in a group increase increase  2009, Prentice-Hall, Inc.

  9. Metals versus Nonmetals Differences between metals and nonmetals tend to revolve around these properties.

  10. Periodic trends • In the periodic table below, draw the periodic trends across a period and in a group using arrows for atomic size (or atomic radius), ionization energy, electron affinity and metallic character.

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