Periodic Trends Ag Chemistry Mrs. Fahey

Ionization The atoms all want to be neutral. The general trend is that the group number determines electrons gained or lost. Atoms will gain or lose electrons to attain the electron configuration of the Nobel Gases. Group 1 loses 1 because it is easier to lose one than to gain 7 in order to have eight outer electrons. Group 7 will gain one electron to have eight. (group 5 gains 3, group 2 loses 2) Elements located in the Transition Elements follow their oxidation numbers. (remember transition elements are rule breakers!)

Atomic Size When an element gains or loses an electron it forms an ion. Elements that gain electrons become negatively charged and are called anions. Elements that lose electrons become positively charged and are called cations. As you proceed down a group, the ion gets bigger. Cations are smaller than the element atom. Anions are larger than the element atom.

Ionization Energy The amount of energy required to remove an electron from an atom is called Ionization Energy. Removing the first electron is called the First Ionization Energy. Removing the second electron is called the Second Ionization Energy and so on. As you proceed down a group, the Ionization Energy decreases. This is because the electrons are farther away from the pull of the protons in the nucleus. As you proceed across a period, the Ionization Energy increases. Electrons are strongly pulled by the increase in protons in the nucleus while the energy level remains the same.

Electronegativity The amount of energy required to add an electron to an atom is called Electronegativity. As you proceed down a group, the Electronegativity decreases. As you proceed across a period, the Electronegativity increases. This is because the electrons are strongly pulled by the increase in protons in the nucleus while the energy level remains the same. These elements have a strong need to fill the outer orbital.