WHAT ARE THE PERIODIC TRENDS?

Periodic Trends• All information in contained in table S• Predictable properties/changes that occur as we move

down groups and across periods• Based on the properties of elements • Repeated from group to group and period to period

Atomic Radius• Size of an atom• Based on the number of protons an atom has and the

number of energy shells• Period Trend:

• As we move left to right atomic radius decreases• As we increase the number of protons the EFFECTIVE NUCLEAR

CHARGE increases (more protons makes an atom stronger)• This is why the smallest elements in a period are always in Group

17• Fluorine is the smallest and strongest element on the table

(Greatest effective charge)

Atomic Radius Cont:• Group Trend:

• As we move down a group atomic radius INCREASES• This is because the number of energy levels increases • Each level adds a shell and so the atom occupies more volume

Ionization Energy• Measurement of how much energy it takes to remove the

outermost electron from an atom• Period Trend:

• Increases moving left to right as the EFFECTIVE NUCLEAR CHARGE increases

• More protons = more nuclear strength • This is why metals lose electrons and non-metals never lose

electrons • Strongest elements are always the non-metals in group 17

Group Trend in Ionization Energy• Group Trend:

• Down a group IE decreases• Each additional energy level makes it more difficult for the nucleus

to hold onto electrons• Francium would be the weakest element

Electronegativity Trends• Measurement of how strongly you attract other elements

electrons to you• Non-metals are good at this, metals are not• Period Trend:

• Same as IE, so across a period electronegativity increases because of increases in EFFECTIVE NUCLEAR CHARGE

• Fluorine is the best (4.0)• This is why non-metals gain electrons and metals lose, greater

attractive forces

Group Trends in Electronegativity• Group Trend:

• Down a group it decreases just like IE• This is because of the effects of adding an energy level (more

volume) • Weakest elements are always at the bottom of a group (most

metallic)• This is again why metals lose electrons and non-metals gain

Trends in Ionic Size• Positive ions are smaller than the atom they came from

due to the loss of an energy level• They always move back to the closest noble gas• Negative ions are always larger than the atom they came

from due to the increase in volume • They always move forward to the closest noble gas• For positive ions, the greater the magnitude of charge, the

smaller the ion (+2 is smaller than +1)• For negative ions, the greater the magnitude of charge,

the larger the ion (-3 is larger than -2)