Periodic Table PBL

Alani, Hannah, Trevor 4th Period Urquhart

Example of a Group from the Periodic Table:

Alkali Metals

The 1st column of the periodic table is the group of elements known as Group 1 or alkali metals. This group includes lithium, sodium, potassium, rubidium, cesium, and francium. The alkali metals have only one (1) electron in their outermost energy level, are the most reactive of all of the metals, and they readily lose their outermost electron to form cations with a charge of +1.

Elements of the Alkali Metals

Example of a Period from the Periodic Table:

Period 2

Even though they skip some squares in between, all of the rows go left to right. When you look at a periodic table, each of the rows is considered to be a different period. In the periodic table, elements have something in common if they are in the same row: All of the elements in a period have the same number of atomic orbitals. Every element in the top row (the first period) has one (1) orbital for its electrons. All of the elements in the second row (the second period) have two (2) orbitals for their electrons. It goes down the periodic table like that. At this time in our lives, the maximum number of electron orbitals or electron shells for any element is seven (7). Also, Dmitri Mendeleev found he could arrange the 65 elements then known in a grid or table so that each element had a higher atomic weight than the one on its left. For example, Beryllium (atomic weight 9.01) is placed to the right of Lithium (atomic weight 6.94)

Trends in the Periodic Table

Moving Left → Right

  • Atomic Radius Decreases
  • Ionization Energy Increases
  • Electronegativity Increases

Moving Top → Bottom

  • Atomic Radius Increases
  • Ionization Energy Decreases
  • Electronegativity Decreases

Trends of the Atomic Radius

Moving from left to right on the periodic table, the atomic radius of an element decreases as the increasing number of electrons pull the shell closer to the positive nucleus. However, as more and more electrons enter the outer shell, repulsion between them begin to exert an effect. The radius will once again increase towards the far right (Group 18), but will never get as large as it was at the far left of the periodic table (Group 1). Moving down the columns, the radius always increases due to the addition of shells.

Trends of the Ionic Radius

What is an Ionic Radius?

- The ionic radius is the measure of an atom's ion in a crystal lattice. Values for ionic radius are difficult to obtain and tend to depend on the method used to measure the size of the ion.

  • Ionic Radius and Group

As you move down a group in the periodic table, additional layers of electrons are being added, which naturally causes the ionic radius to increase as you move down the periodic table.

  • Ionic Radius and Period

As you move across a row of period of the periodic table, the ionic radius decreases for metals forming cations, as the metals lose their outer electron orbitals. The ionic radius increases for nonmetals as the effective nuclear charge decreases due to the number of electrons exceeding the number of protons.

  • Ionic Radius and Atomic Radius

The ionic radius is different from the atomic radius of an element. Positive ions are smaller than their uncharged atoms. Negative ions are larger than their atoms.

Average Atomic Mass

The average atomic mass of an atom is found by averaging over the natural abundances of its isotopes.

  • Example:

6Li 6.015 amu 7.42% & 7Li 7.016 amu 92.58%

Avg. mass = (6.015 amu * 0.0742) + (7.016 amu * 0.9258) = (6.941 amu)