Course: AP Biology
Topic: Atoms and Ions
Warm-up: Draw an atom and label these parts: electron, proton, neutron, nucleus, orbital (5 minutes)
-Review some of the chemical elements by building models of atoms
-Review basic chemistry vocabulary and concepts: protons, neutrons, electrons
-Review ionic bonds
-12 Laminated atomic models, 25-30 m&m’s per group, copies of periodic table, paper cups
Activity 1: (20 minutes)
1.) Sort the candy by color and place into paper cups. Place 3 colors of candy at each lab table.
2.) Using the periodic table, one nucleus and one orbital, have each student make a helium atom showing number
of protons, neutrons, electrons using the M&M’s. Students draw atom and label in notes.
3.) Before discussing aloud, ask each student to jot down in their notes what this atom would be called if the
proton, electron or neutron number changed. Discuss their answers and discuss the following points:
a. A change in the number of protons= a new element
b. A change in the number of electrons= a charged ion
c. A change in the number of neutrons= an isotope (Radioisotopes)
4.) Discuss atomic mass and atomic number
5.) Students build a hydrogen atom with paper models. Ask students to make changes listed above and record in
notes how it changes the atom.
6.) Discuss the number of electrons that fit in each orbital and have students build models and record in their notes
the following atoms: C, N, O and F
7.) Discuss electronegativity and ask the students to note trends on their periodic table. (Electronegativity increases
from left to right across a row and decreases from top to bottom in a column)
8.) Socratic discussion:
a. How many electrons fit in each orbital?
b. How does the proton number compare to the electron number?
c. How do you think the number of electrons on the outer orbital of each atom relates to how stable the
d. Which elements are the most stable?
e. Which elements are most reactive?
Activity 2: Ionic Bonds
1.) Using paper atomic models build a fluorine and hydrogen atom.
2.) Talk about atom stability and have them move electron from hydrogen to fluorine to make stable and form an
3.) Students draw a before and after diagram in notes.
4.) Build the following compounds- LiCl, MgO and BeS
a. In each of the molecules built which atom became the cation and anion?
b. Which elements of the periodic table tend to become negative ions?
c. Which elements of the periodic table tend to become positive ions?
d. Which columns would combine well in order to be more stable?
e. Which elements on the periodic table tend to make ionic bonds?
f. How does electronegativity relate to ionic bonds?
g. Why don’t all elements of the periodic table form ionic bonds?
h. What do atoms that cannot form ionic bonds do to become more stable?
Elements -substance that cannot be broken down by chemical
-Essential elements to life—C, O, H, N
Compounds -2 or more elements bonded
-Example NaCl (sodium chloride)
He (Helium) Atomic number = # number of protons Atomic mass=
Protons + Neutrons
a.) Change in # of protons= new
b.) Change in # of electrons = charged
ion (cation +, anion -)
c.) Change in # of neutrons= isotope
Isotope same number of protons different number of neutrons
Radioactive isotope unstable nucleus, decays and gives off particles and
Electronegativity atoms ability to attract electrons
-Increases from left to right across a row and top to
bottom on a column of the periodic table
# of electrons in each orbital - 2 inner s orbital, 8 on the next 2 p orbitals
Protons vs. Electrons -Protons and electrons are equal in number if the atom is
-If proton number and electron number is different an ion
-Cation- less electrons (positive charge)
-Anion- more electrons (negative charge)
How does the number of electrons in outer orbital -More electrons in valance shell (outermost orbital) allows
determine stability of atom? atom to be more stable
-Atom always wants its orbitals to be filled to capacity with
Which elements are more stable? (VIII) -Noble gases- outer orbital filled to capacity
Which elements most reactive? -Halogens (VII)
Ionic Bonds HFl- forms an ionic bond
-Hydrogen gives an electron to fluorine to full fill fluorine
Ionic bond- bond formed from stealing an electron
In the compounds LiCl, MgO, BeS, which atoms become -Cation- Li, Mg, Be
cations or anions? -Anion- Cl, O, S
Elements of the periodic table tend to become negative -Those with the greatest potential to gain electrons—high
-Column VII- halogens Why? Missing only one electron,
have a high electronegativity
Elements of periodic table tend to become positive ions: -Those with the least potential to gain electrons- low
-Farthest column to the left- Why? Have only 1 electron in
Columns that combine well to form more stable -Column I and Column VII, Column II and Column VI
Electronegativity relates to ionic bond because: -Atoms with high electronegativity are able to steal
electrons more easily
-Atoms with low electronegativity are more willing to have
Why don’t all atoms form ionic bonds? -At some point an element is too unstable to steal or have
stolen an enough electrons to become stable—too little or
too much electronegativity preventing necessary exchange
What do atoms that cannot form ionic bonds do to -Form covalent bonds
become more stable?