Periodic Trends

Shielding Effect Inner electrons: electrons between the nucleus and the outermost energy level. The inner electrons shield the valence electrons (outermost electrons) from the positive charge of the nucleus. This causes a reduction in attraction between the nucleus and the valence electrons so that the valence electrons are held more loosely.

Shielding Effect Increases Stays the same

Atomic Radius The atomic radius is the distance from the atomic nucleus to the atom’s outer “surface”. The atomic radius gets gradually smaller with increasing atomic number.

6.3 Trends in Atomic Size The size of atoms tends to decrease from left to right across a period and increase from top to bottom within a group. Predicting If a halogen and an alkali metal are in the same period, which one will have the larger radius?

Ions Positive Ion Negative Ion An ion is a charged atom. Ions have unequal numbers of electrons and protons. If a neutral atom loses electrons, its protons will outnumber its electrons. (Positive Ion) If a neutral ion gains electrons, its electrons will outnumber the protons. (Negative Ion) Positive Ions are called Cations (metals) Negative ions are called anions (nonmetals) Negative Ion

Ionic Radius When metals lose electrons they become smaller due to the nuclear charge being larger than the number of electrons. Electrons are held tighter. When nonmetals gain electrons they become larger due to the nuclear charge being less than the number of electrons. Electrons are held looser.

Trends in Ionic Size 6.3 Trends in Ionic Size Size generally increases The ionic radii for cations and anions decrease from left to right across periods and increase from top to bottom within groups.

Ionization Energy the amount of energy required to pull an electron away from an atom to form a positively charged ion.

Trends in Ionization Energy 6.3 Trends in Ionization Energy First ionization energy tends to increase from left to right across a period and decrease from top to bottom within a group. Predicting Which element would have the larger first ionization energy—an alkali metal in period 2 or an alkali metal in period 4?

Electronegativity Electronegativity is thought of as an atom’s “electron pulling power.”

Electronegativity The greater an atom’s electronegativity, the greater its ability to pull electrons towards itself when bonded. . Fluorine has the highest electronegativity.

Trends in Electronegativity INCREASES Decreases