The Periodic Table When Dimitri Mendeleev developed the Periodic Table, he grouped elements according to their physical properties. As it turns out, there is a pattern of repeating chemical and physical properties among the different groups of elements on the period table. There is a trend among atomic size, nuclear pull on the electrons, ionization energy, and electronegativity.

The Periodic Table Periodic Table terms Groups A vertical column on the period table. Sometimes referred to as ‘family’. All of the elements in the same group have very similar chemical and physical properties. All element within the same group have the same number of valence electrons.

The Periodic Table Periodic Table terms Periods Horizontal rows on the Periodic Table. Each Period represents an additional quantum. There is a repeating pattern of chemical and physical properties as you move from left to right, up to down on the Periodic Table.

The Periodic Table Periodic Table terms Valence Electrons Are the outer most electrons in the last p-sublevel and s- sublevel in the same highest quantum. They are responsible for the chemical reactiveness of an element. The number of valence electrons that an element has is the same as the group number.

The Periodic Table Periodic Trends Effective Nuclear Charge (Z) A measure of the ‘pull’ on the electrons from the atomic nucleus. All of the other trends are based on this concept. Increase in effective nuclear charge Decrease in effective nuclear charge

The Periodic Table Periodic Trends Effective Nuclear Charge (Z) Increase from left to right because the there is an increase in the number of protons within the atomic nucleus. Decreases from top to bottom because with the addition of more quantums, there is a larger distance between the atomic nucleus and the electrons. Increase in effective nuclear charge Decrease in effective nuclear charge

The Periodic Table Periodic Trends Atomic Radii Half the distance between two nuclei in a diatomic molecule. It represents the distance between the atomic nucleus and the other electrons.

The Periodic Table Periodic Trends Atomic Radii As you move from right to left on the Periodic Table, the atomic radii decreases because the effective nuclear charge increases. As you move from top to bottom on the Periodic Table, the atomic radii increases because the elements have more quantums.

The Periodic Table Periodic Trends Atomic Radii

The Periodic Table Periodic Trends Ionization Energy – The amount of energy required to remove an atom’s outermost electron.

The Periodic Table Periodic Trends Ionization Energy As you move from left to the right on the Periodic Table, the Ionization energy increases because Z increases. As you move from the top to the bottom of the Periodic Table, ionization energy decreases because there is more distance between the atom and the valence electrons.

The Periodic Table Periodic Trends Ionization Energy 1 st Ionization Energy – The amount of energy required to remove the 1 st valence electrons. 2 nd Ionization Energy – the amount of energy required to remove the 2 nd valence electrons.

The Periodic Table Periodic Trends Electronegativity A measure of how a nucleus can ‘pull’ on the electrons of another atom when it forms a compound with other elements. Electronegativity is expressed as a number without any units.

The Periodic Table Periodic Trends Electronegativity From left to right on the Periodic Table, electronegativity increases. Why? Up to down on the Periodic Table, electronegativity decreases. Why?