Unit 3 – Lesson 3 Periodic Table

Lesson 3 . Periodic Table Trends There are 109 individual squares, each showing the element name, element symbol, atomic number and atomic mass. Some tables show more information.

Atomic Radius Distance from the center of the nucleus to the outermost orbital Atoms get larger going down a group because each is one energy level bigger (“n” increases) Atoms get smaller going across a period because more protons (+) are pulling the electrons towards the nucleus (greater Z efficiency) Z Efficiency: As you increase the number of protons in the nucleus of the atom, you increase the effective nuclear charge of the atom (Zeff), and the nucleus pulls more strongly on the entire electron cloud. This makes the atomic radius decrease in size. Distance from center of an atom to the outermost electron This distance must be estimated since the atom is not solid http://www.youtube.com/watch?v=ba2yN2HtPTA&feature=related

Atomic Radii Decrease in atomic radius (generally) Increase in atomic radius (generally)

Ionic Radius Size of ions Atoms that lose electrons, lose their whole outer shell, thus they become smaller. Atoms that gain electrons become bigger because the extra electrons repel each other and space out more. Ions are atoms that gain or lose electrons to get a full outer shell http://www.youtube.com/watch?v=hkyxQjKwBU4

Ionic Radii negative ions decrease Positive ions decrease Increase in ionic radius (generally) Largest negative ion As3- Largest positive ion Fr +

Ionization Energy Energy needed to pull off one electron (make an atom an ion) from a gaseous atom. The higher the ionization energy, the more difficult it is to remove an electron Atoms with a small atomic radius have a large ionization energy. Why? – if the radius is small, the nucleus has a larger attractive force on the electron. Atoms with a large electronegativity have a large ionization energy. Why? –If the atom wants to gain electrons, it is going to be very difficult to take electrons from it. Octet Rule – 8 electrons in outer shell. H and He only need 2 electrons. Metals lose there outer shell to get a full stable ion. Nonmetals gain electrons to get a full outer shell. http://www.youtube.com/watch?v=LxXqLzK9vmY

First Ionization Energy Increase in first ionization energy (generally) Decrease in ionization energy (generally)

Electronegativity Ability to attract electrons in a chemical bond Electronegativity increases from left to right across a period Why? – Elements on the right side of the periodic table have a larger (+) charge in the nucleus and are closer to attaining 8 valence electrons Electronegativity decreases as you go down a group Why? – As you move down the table the valence electrons get further from the (+) nucleus http://www.youtube.com/watch?v=93G_FqpGFGY

Electronegativity Increase in electronegativity Noble gases are left out since they are not known to readily form compounds Electronegativity Increase in electronegativity F is the most electronegative Decrease in electronegativity Fr is the least electro-negative

Summary Francium, Fr Large radius Low ionization energy Low electronegativity Fluorine, F Small radius High ionization energy High electronegativity

Sample Problem (a) aluminum (b) carbon Boron, carbon, and aluminum occur near each other in the periodic table. Use the periodic table to identify which of these elements is (a) the largest atom, and (b) the atom with the highest ionization energy. (a) aluminum (b) carbon

Examples Compare the following atoms: F, Br, At Which has the largest: Electronegativy? Atomic Radius? 1st Ionization energy?

Examples Compare the following atoms: K, Cu, Kr Which has the largest: Electronegativy? Atomic Radius? 1st Ionization energy?

Trends in Metallic Character Metals have a higher tendency to lose electrons in order to achieve the stability of a filled octet Valence electron farther from nucleus = easier to lose electrons As electronegativity or ionization energy increases, metallic character decreases

Trends in Metallic Character Metals have a higher tendency to lose electrons Valence electron farther from nucleus = easier to lose electrons