Download 2 IONS

#1 ATOMIC SIZE – decreases across and increases down the
periodic table
#2 IONSLeft side of the periodic table forms positive ions.
Group 1- charge of +1 (lose an electron)
Group 2- charge of +2 (lose 2 electrons)
Groups 3-12 (form positive ions with varying charges)
Group 17-charge of -1 (gain an electron)
Group 16-charge of -2 (gain 2 electrons)
Group 18 do not form ions
1. Trend in Atomic Size
•Label your periodic table neatly. (Down the group,
increase atom size.) (Left to right across the period,
decrease atom size.)
#1 ATOMIC SIZE – decreases across and increases down the periodic table
#2 IONSLeft side of the periodic table forms positive ions.
Group 1- charge of +1 (lose an electron)
Group 2- charge of +2 (lose 2 electrons)
Groups 3-12 (form positive ions with varying charges)
Group 17-charge of -1 (gain an electron)
Group 16-charge of -2 (gain 2 electrons)
Group 18 do not form ions
Ions:


Because electrons are on the outside, sometimes
electrons can be gained from or lost to another atom.
These atoms are called ions.
 Cations are positive (LOST ELECTRON) and are formed
by elements on the left side of the periodic chart.
 Anions are negative (GAINED ELECTRON) and are
formed by elements on the right side of the periodic
chart.
Practice finding the parts of an atom:
Element
24Mg+1
12
39K+2
19
23Na+1
11
19F-1
9
27Al+3
13
32S-2
16
24 Mg+2
12
Atomic #
Atomic
Mass #
# of
Protons
# of
# of
Neutrons Electrons
Periodic Table:

1 e1+
Label your periodic table like the one below!
•Top # = # of electrons (e-) in the outer most shell (valence shell)
2e2+
•Bottom # = ionization #
4e- 5e- 6e- 7e4- 3- 2- 1-
8e0
2. Trend in Ionization Potential
Ionization potential = how hard they hold on to their
electrons in the valence shell.
Largest toward NE corner of PT since these atoms hold on
to their valence e- the tightest.
2. Trend in Electron Affinity
Electron Affinity = how much they want to steal
someone else’s electrons!
Most favorable toward NE corner of PT since these atoms
have a great affinity for e-.
Summary of Trend: Draw these neatly on your periodic
tables.
2. Ionization Energy: Largest toward NE of PT
3. Electron Affinity: Most favorable NE of PT
1. Atomic Radius: Largest toward SW corner of PT