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Periodic Properties
Chemical and physical properties of the elements change with their position
in the periodic table.
General Information
• 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
• Within a period, atoms generally get smaller as you move from left to right.
• WHY?
Because of the increasing positive charge (more protons) of the nucleus.
Trend in Atomic Size
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
• Cations (positively charged)– The atom has LOST electrons to become positively
charged (more protons than electrons)– They are SMALLER than the neutral atom of the
same element
• WHY?The valence electrons
are lost, along with
the entire outer shell.
Trend in Ionic Size
• Anions (negatively charged)– The atom has GAINED electrons to become negatively
charged (more electrons than protons)– They are LARGER than the neutral atom of the same element
• WHY?The protons in the nucleus
cannot pull in the increased
Negative charge and the
added electrons are
repelling each other,
pushing them farther apart
Trend in Ionic Size
Ionization Energy
The amount of energy needed to remove one valence electron from an atom of an element.
• 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
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.
• 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.
Trend in Electronegativity