Periodic Properties Chemical and physical properties of the elements change with their position in the periodic table.
Review • Group = column • Period = row • Octet Rule • atoms tend to gain, lose, or share electrons in order to gain 8 valence electrons (full outer shell), like Noble gases • An element with a full valence shell is a happy element
Atomic Size Distance from the center of an atom's nucleus to the edge of its electron cloud. atom
Trend in Atomic Size • Within a period, atoms generally get smaller as you move from left to right. • WHY? Because of the increasing positive charge of the nucleus.
Trend In Atomic Size • Within a group, atoms generally get larger as you move from top to bottom. • WHY? Electrons are added to energy levels further from the nucleus.
Dr. Lanzaflame; Atomic radii; www.monroecc.edu/wusers/flanzafame/PerRadii.pdf
Ionization Energy The amount of energy needed to remove one valence electron from an atom of an element.
Trend in Ionization Energy • Within a period, IE increases as you move from left to right. • WHY? • Elements on the right of the chart want to take electrons, so they do not want to donate any. • Elements on the left of the chart would prefer to give up their electrons so it is easy to remove them.
Trend In Ionization Energy • Within a group, IE decreases as you move from top to bottom. • WHY? • The farther away from the nucleus an electron is, the easier it is to remove because the positive charge of the proton has less hold on the negative charge of the electron.
Electronegativity • The tendency of an atom to attract electrons to itself in a chemical bond.
Trend in Electronegativity • Within a period, EN increases as you move from left to right. • WHY? • Elements on the left of the period table would rather give electrons away than take another atom's electrons. • Elements on the right side of the period table only need a few electrons to complete the octet, so they have strong desire to take another atom's electrons.
Trend in Electronegativity • Within a group, EN decreases as you move from top to bottom. • WHY? • Elements near the top of the period table have few electrons, so every electron is a big deal. • Elements near the bottom of the chart have so many electrons that loosing or taking an electron is not as big a deal.
Reactivity Reactivity refers to how likely an atom is to react with other substances.
Trends in Reactivity • Metals • Period - reactivity decreases as you go from left to right across a period. • Group - reactivity increases as you go down a group • Why? • To react, metals needs to get rid of electrons, thus they need a low IE.
Trends in Reactivity • Non-metals • Period - reactivity increases as you go from the left to the right across a period. • Group - reactivity decreases as you go down the group. • Why? • For nonmetals to react, they must gain electrons, so they need a high EN.