Discovering and understanding patterns in the P.T. Discovering and understanding patterns in the P.T.

Objective: To discover the periodic trends of certain physical properties of elements related to their position on the Periodic Table of Elements. Background: The Periodic Table is arranged according to the Periodic Law. Periodic Law states that when elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic pattern. You will discover this by examining the changes in properties of elements on the Periodic Table.

Atomic Radius The Atomic radius is the distance from the center of the atom’s nucleus to the outermost electron

Atomic Radius and Ionic Radius Why is there a difference in radius size between the Na/Mg elements and the [Na] +1 / [Mg] +2 ions?

Ionization Energy Ionization energy is the energy needed to remove one of it’s electrons. Think of this as how tightly the atom is holding on to its’ electrons. If it holds on tight, Ionization energy is high, and conversely, if ionization energy is low, the atom will give up an electron easily. First ionization energy is the energy required to remove the first electron. Successive ionization energies are those required to remove additional electrons from an atom.

Electronegativity Electronegativity has to do with an atom's ability to attract electrons when it bonds with another atom. In common terms it’s electron greediness!

Electron Affinity The energy change that occurs when an atom gains an extra electron and becomes an anion. For example, the electron affinity for Fluorine is –228 kJ/mol. Why is the number negative? Fluorine does not need energy to gain an electron, there is sufficient energy available within the fluorine atom to accept the electron and so it releases the extra energy!

Valence This is a number indicating the number of electrons which will be gained or lost when it bonds to another atom (also called its oxidation #). When an atom gains or loses electrons it is called an ion. Positive ion (loses e - ’ s ) = cation “Plussy Cat” Negative ion (gains e - ’ s ) = anion

6 Periodic Trends The Final word That’s just another way of saying we’re not done yet and you better remember this! That’s just another way of saying we’re not done yet and you better remember this!

Periodic Trends A periodic trend is a property that changes predictably as you move across a period and down a Family in the periodic Table.

Periodic Trends Atomic Radius The size of the atom measured from the center of the nucleus to the outer most electron. Atomic Radius Decreases Atomic Radius Increases

Atomic Radius As you move from left to right across a period atomic radius decreases since we are adding more protons and electrons. As these particles are added, the attractive force between the particles increases and the electrons get pulled closer to the nucleus and the atom gets smaller. As you move from top to bottom of a family you are also adding electron orbitals and the atom gets bigger.

Periodic Trends Valence Valence is a number indicating the atoms’ tendency to gain or lose e -’s during the bonding process Valence Varies

Valence As a general rule, valence shows a pattern in families 1A-8A. This pattern exists because of each of the elements desire to have a full octet thus looking like a noble gas. When you consider the transition metals, the pattern no longer exists.

Periodic Trends Electronegativity The property of an atom which describes its ability to attract e -’s in a chemical bond. Electronegativity Increases Electronegaticvity Decreases

Electronegativity Electronegativity is directly related to atomic radius and ionization energy. As we move across the period the atomic radius decreases and since the electrons are closer to the nucleus, they are held very tightly and require large amounts of ionization energy in order to remove an electron. The tendency for atoms with high electronegativity is to hold very tightly to the electrons within a bond. As we move down a Family there is a decrease again partially due to a radii increase.

Periodic Trends Ionization Energy The energy required to remove e -’s creating an cation. Ionization Energy Increases Ionization Energy Decreases

Ionization energy Ionization energy is directly related to atomic radius. As we move across the period the atomic radius decreases and since the electrons are closer to the nucleus, they are held very tightly and require large amounts of ionization energy in order to remove an electron. As we move down a family the atoms radius increases so therefore it doesn’t require as much energy to remove an outer electron.

Periodic Trends Electron Affinity The energy change that occurs when an atom gains an e - and become a anion. Electron Affinity Increases Electron Affinity Decreases

Electron Affinity Electron Affinity is the measure of an atom’s attraction for an additional electron. As a general rule, the atoms of nonmetals electron affinity (except for the Noble gases), are more negative than for metals. In other words, nonmetals tend to have a higher affinity for electrons than do metals. This is in part due to both their position in the table and the size of their radii.

Periodic Trends Metallic Properties Included are elements that are soft solids at room temp, having the property to conduct electricity & have magnetic attraction. Metals Nonmetals Metalloids Metallic Properties Decrease Metallic Properties Increase

Metallic Properties Metallic properties include, being soft solids at room temperature (with the exception of mercury), conductors of heat and electricity, being attracted to a magnet, malleable and ductile, high melting points with high luster and shine.

Each of the 6 trends described are properties that change in a predictable manner as you move across a period and down a Family in the periodic Table.

We will now complete a reciprocal teaching & learning activity to help your learn these Trends.