Study Guide 2.1-2.8
2.1-2.2
Write the chemical symbol for each of the following elements and state whether it is one of the four elements used in large amounts
(L), moderate amounts (M), or whether it is a trace element (T) and is required in small amounts.
Mg
O
Cu
Ca
H
M
L
T
M
L
1.
2.
3.
4.
5.
Magnesium
Oxygen
Copper
Calcium
Hydrogen
C
Fe
Na
N
K
L
T
M
L
M
6.
7.
8.
9.
10.
Carbon
Iron
Sodium
Nitrogen
Phosphorus
11. Give a specific example of what can happen if you do not get one of the trace elements in your diet.
No iodine=no production of thyroid hormone=enlargement of thyroid (goiter)
2.4-2.6
After reading about the structure of atoms, fill in the following chart. First fill in the blanks. Then sketch each atom, labeling and
coloring the protons red, neutrons grey, and electrons blue.
Element
Symbol
Mass number
C
Atomic
number
6
12
Number of
protons
6
Number of
neutrons
6
Number of
electrons
6
Carbon-12
Nitrogen-14
7 protons and 7 neutrons
in nucleus. 2 electrons in
the first electron shell. 5
electrons in the second
electron shell
Chlorine-35
N
7
14
7
7
7
Cl
17
35
17
18
17
O
8
16
8
8
8
17 protons and 18
neutrons in the nucleus.
2 electrons in the first
electron shell. 8
electrons in the second
electron shell and 7
electrons in the third
electron shell
Oxygen-16
8 protons and 8 neutrons
in nucleus. 2 electrons in
the first electron shell, 6
electrons in the 2nd
electron shell
Element
Symbol
Oxygen-17
8 protons and 9 neutrons
in nucleus. 2 electrons in
the first electron shell, 6
electrons in the 2nd
electron shell
O
Atomic
number
8
Mass number
17
Number of
protons
8
Number of
neutrons
9
Number of
electrons
8
This is an ISOTOPE of the
oxygen atom described
above
2.6-2.8
The four atoms shown below are important to life. Look closely at their electron shells. Remember that if an atom has an unfilled
outer electron shell it will undergo a chemical reaction in order to fill that shell. The first shell is complete at 2 and for biologically
important elements 8 is the magic number to fill the outer shell.
1.
Given the information above and the diagrams, show how electrons would be transferred between calcium and chlorine
atoms to form calcium and chloride ions, which would then attract each other to form calcium chloride, CaCl2 (hint: An
atom can gain or lose more than one electron)
Calcium has 2 electrons in its outer electron shell. If it can get rid of these, it will be stable. Chloride has 7 electrons in its outer
electron shell and needs one more electron to be stable. A chloride atom will take one of calcium’s extra electrons making it a
negative ion. A second chloride atom will take the last electron from calcium also becoming a negative ion. Calcium has lost its two
outer electrons and becomes a positive ion (with 2 positive charges). The positive calcium is attracted to the two negative chlorides
forming an ionic bond
2.
Using the info and diagrams above, show how nitrogen could form covalent bonds with several hydrogen atoms, forming a
molecule of ammonia. What would be the molecular formula for ammonia?
Nitrogen has 5 electrons in its outer electron shell and needs 3 more. Hydrogen has one electron and needs one more. A
hydrogen can share its one electron with nitrogen and nitrogen can share one of its electrons with hydrogen. This H is now
stable, but N has only 6 electrons in its outer shell. A second H can come in and share its electron, becoming stable and
giving N 7 electrons. A third H can share its electron becoming stable and allowing N to be stable with 8 electrons in the
outer shell. Molecular formula is NH3.