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Atomic Radius

Atomic Radius. The radius of an atom . Periods - decreases as you move left to right across the table Why? Nucleus becomes more positive , while the electrons remain in the same energy level. This change causes the electrons to be pulled toward the nucleus making the radius smaller .

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Atomic Radius

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  1. Atomic Radius • The radius of an atom. • Periods - decreases as you move left to right across the table • Why? Nucleus becomes more positive, while the electrons remain in the same energy level. This change causes the electrons to be pulled toward the nucleus making the radius smaller. • Groups - increase as you move down a group. • Why? More energylevels are added to the atom making it bigger.

  2. Which of the following has the largest atomic radius? • F or Br • Al or S • Na or P • Li or Rb

  3. Ionic Radius • The radius of an ion. • Ion – an atom with a negative or positive charge (gained or lost an electron) • Important: When an atom gains / loses electrons, it becomes more negative / positive and then becomes bigger / smaller. • Periods – • The left side has positively charged ions. • The right side has negatively charged ions. • Where they meet, there is a huge jump in ionic radius. • Groups - increase as you move down a group. • Why? More energylevels are added to the atom making it bigger.

  4. Another way to think of it: The more negative the bigger; the more positive the smaller

  5. Which of the following has the largest ionic radius? • Sr+2 or Rb+1 • Br-1 or F-1 • Ti+2 or Se-2

  6. For the next two trends, remember the octet rule. (All atoms want 8 valence electrons)

  7. Ionization energy • Energy required to remove an electron or how well an atom’s nucleus holds onto its valence electrons. • Periods - increases as you move left to right across the table • Why? more nuclear charge strongly hold on electrons • Groups - decrease as you move down a group. • Why? more electrons are further from the nucleus resulting in less pull. • This is also caused by electronshielding - the blocking of the positive nucleus by inner electrons.

  8. Which of the following has the highest ionization energy? • N or As • B or O • Li or Rb • Be or Sr

  9. Electronegativity • Relative ability of an atom to attract electrons in a chemical bond. • Periods - increases as you move left to right across the table • Why? more nuclear charge attract electrons • Groups – decrease as you move down a group. • Why? Electrons are further from the nucleus resulting in less attraction. • Not counting the noblegases (Group 8A), fluorine is the most electronegative while francium is the least.

  10. Which of the following has the highest electronegativity? • Na or Rb • B or F • K or Ca • F or I

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