Atomic Radius The radius of an atom. The radius of an atom. Periods - decreases as you move left to right across the table 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. 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. Groups - increase as you move down a group. Why? More energy levels are added to the atom making it bigger. Why? More energy levels are added to the atom making it bigger.

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

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

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

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

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

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

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

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

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