1. Background Losing an electron is called ionization
04/10/99
Losing an electron is called ionization
An ion is an atom that has either a net positive or net negative charge
Q: what would the charge be on an atom that lost an electron? Gained two electrons?
A: +1 (because your losing a -ve electron)
A: -2 (because you gain 2 -ve electrons)

2. Atomic Radius Trend
Group Trend – As you go down a column, atomic radius increases
As you go down, e- are filled into orbitals that are farther away from the nucleus (attraction not as strong)
Periodic Trend – As you go across a period (L to R), atomic radius decreases
As you go L to R, e- are put into the same orbital, but more p+ and e- total (more attraction = smaller size)

3. Ionization Energy
Ionization Energy – energy needed to remove outermost e-

4. Ionization energy
04/10/99
Ionization energy is the energy required to remove one outer electron from an atom
Note: atomic radius is the distance from the nucleus to the outer electron shell
Ignore H when looking at trends, look at many periods/groups when summarizing trends
Group Trend – As you go down a column, ionization energy decreases
As you go down, atomic size is increasing (less attraction), so easier to remove an e-

5. Ionization Energy
As you go down, atomic size is increasing (less attraction), so easier to remove an e-
Periodic Trend – As you go across a period (L to R), ionization energy increases
As you go L to R, atomic size is decreasing (more attraction), so more difficult to remove an e-
(also, metals want to lose e-, but nonmetals do not)

6. Ionization energy vs. atomic number
04/10/99

7. Atomic radius vs. atomic number
04/10/99

8. electron configuration of Na+ resembles Ne
04/10/99 7.
11p+ 12n°
11p+ 12n°
10p+ 10n°
Na has 11 electrons
Na+ has 10 electrons
Ne has 10 electrons
electron configuration of Na+ resembles Ne
Alkali metals become like noble gases
Radius increases because shells are added
Increased radius will make it easier to lose an electron because of greater distance between positive and negative charges

9. Li (enc = 1) Be (enc = 2) B (enc = 3) + + + + + + + + + + + +
9. Proton # increases. More protons means greater attraction between nucleus and outer electron thus higher ionization energy.
The greater attraction also means that outer electrons are brought closer to the nucleus, thus smaller atomic radius results.
04/10/99
Li (enc = 1)
Be (enc = 2)
B (enc = 3) + + + + + + + + + + + +

10. Li (enc = 1) Be (enc = 2) B (enc = 3) + + + + + + + + + + + +
9. Proton # increases (1). More protons means greater attraction between nucleus and outer electron (1) thus higher ionization energy.
The greater attraction also means that outer electrons are brought closer to the nucleus, thus smaller atomic radius results.
04/10/99
Li (enc = 1)
Be (enc = 2)
B (enc = 3) + + + + + + + + + + + +

11. Reactivity Reactivity – tendency of an atom to react
Metals – lose e- when they react, so metals’ reactivity is based on lowest Ionization Energy (bottom/left corner) Low I.E = High Reactivity
Nonmetals – gain e- when they react, so nonmetals’ reactivity is based on high electronegativity (upper/right corner)