Atomic Size, Ionization Energy, & Electronegativity Periodic Table Trends Atomic Size, Ionization Energy, & Electronegativity 1.c. – Students know how to use the periodic table to identify alkali metals, alkaline earth metals and transition metals, trends in ionization energy, electronegativity, and the relative sizes of ions and atoms.

Periodic Law Mendeleev understood the ‘Periodic Law’ which states: “When arranged by increasing atomic number, the chemical elements display a regular and repeating pattern of chemical and physical properties”.

Are Elements in a Row or Period Alike? Periodic Law Continue Atoms with similar properties appear in groups or families (vertical columns) on the periodic table. They are similar because they all have the same number of valence (outer shell) electrons, which governs their chemical behavior. Are Elements in a Row or Period Alike? Families or Groups share similar chemical and physical properties!

Periodic Law Continue There are several other important atomic characteristics that show predictable trends that you should know. Atomic size Ionization Energy Electronegativity

WHY DO ATOMS GET BIGGER AS YOU GO DOWN A GROUP? Atomic Size WHY DO ATOMS GET BIGGER AS YOU GO DOWN A GROUP? Atoms at the bottom of the periodic table are BIGGER than atoms at the top!

Energy Levels are Added…Making the Atom Bigger! 1 2 3 Energy Levels are Added…Making the Atom Bigger! 4 E7 5 6 E6 E5 7 E4 E3 E2 E1 nucleus

What happens as we go across a Period? As we go down a group each atom has another energy level…So the atoms get bigger. H Li Na What happens as we go across a Period? K Rb

what increases as we go across a row? Atoms on the left side of the periodic table are bigger than atoms on the right side of the periodic table. what increases as we go across a row?

As we move across a period…. protons are added… As we move across a period….protons are added….this increases the nuclear charge (+)! As protons are added….electrons are also added….so the electrostatic attraction increases (positive & negative attraction)! This attraction pulls the outermost electrons in closer to the nucleus….making the atom smaller! Na Mg Al Si P S Cl Ar _ _ + +

Atomic Size Increases Atomic Size Increases Atomic size tends to increase from right to left and from top to bottom. Atomic Size Increases Atomic Size Increases

Ionization Energy Ionization Energy - amount of energy needed to remove an electron from an atom. Is it harder to take electrons from elements that want to lose e- or elements that wants to gain e-?

Medium-High IONIZATION ENERGY Very High IONIZATION ENERGY It is harder to remove an electron from smaller atoms because the nucleus is closer and better able to hold on to them. It is easier to take electrons from larger atoms because the electrons are further from the nucleus. It is easier to take electrons from metals since they want to LOSE electrons! Alkali metal Noble Gases LOW IONIZATION ENERGY Medium-High IONIZATION ENERGY Very High IONIZATION ENERGY Halogens

Ionization Energy tends to increase from left to right and from bottom to top.

Electronegativity Electronegativity - ability of an atom to attract an electron.

Which element has the highest electronegativity? It is easier for small atoms to attract an electron because the nucleus is closer and is better able to hold on to them. It is easier for nonmetals to gain electrons. Which element has the highest electronegativity?

Electronegativity tends to increase from left to right and from bottom to top.

Putting It All Together Metals Metalloids (Semimetals) Nonmetals Left Side Alkali Alkaline Earth Transition Elements dividing the metals and nonmetals (stair-step line) Right Side Halogens Noble Gases Give up (Lose) e- Cations Or Accept (Gain) e- Accept (Gain) e- Anions Big Atomic Size Small Atomic Size Low Ionization High Ionization Low Electronegativity High Electronegativity (Excluding Noble Gases) (Noble gases do not gain e-)

Cornell Questions As you move across a Period, how does the atomic number change? As you move across a Period, how does the “pull” of the nucleus on the electrons change? As you move across a Period, how does the atomic size, ionization energy, and electronegativity change? As you move down a Group, how does the atomic size, ionization energy, and electronegativity change?

Atomic Size Increases Increases

Ionization Energy Electronegativity Increases Electronegativity Increases

Create a Periodic Table Trends Periodic Table Number the rows and groups Draw increasing arrows representing atomic size (must be in color) Draw increasing arrows representing ionization energy (must be in a different color) Draw increasing arrows representing electronegativity (must be in a different color)