Download The Atom

What is an Atom?
Data collected from selected atoms.
1 amu = 1.6606 x 10-24 g
Electron (-)
Proton (+)
Neutron
(neutral)
A
12
Z X
6C
A is the mass number
Z is the atomic number
The nucleus of an atom contains the protons and the neutrons.
1
H and 2H are isotopes of hydrogen.
12
C and 13C are isotopes of carbon.
An ion is a charged particle, O2- and Na+ are ions.
You can’t see all the neutron and protons in the nucleus in the diagrams
Adapted from Chemistry a Guided Inquiry and NCSSM Guided Inquiry
Chemists identify isotopes by using a mass spectrometer. The
separation is possible because each isotope has a different mass.
Lighter masses will bend more as they pass through the magnet field.
Critical Thinking Questions
1. How many protons are found in
12
C?_______
2. How many neutrons are founds in
3. How many electrons are found in
12
12
13
C?_____
C?____
13
C? ____13C- ?____
13
C? ____13C- ?____
C?_____
13
C- ?____
4. Based on the data presented above,
a. What do all carbon atoms (and ions) have in common?
b. What do all hydrogen atoms (and ions) have in common?
5. What is the significance of the atomic number, Z? Where will you
find it on the periodic table?
6. Look at a periodic table, what do all nickel (Ni) atoms have in
common?
Adapted from Chemistry a Guided Inquiry and NCSSM Guided Inquiry
7. How is the mass number, A, determined?
8. What structural feature is different in isotopes of a particular
element?
9. What feature distinguishes a neutral atom from an ion?
10.
Where is most of the mass of an atom, within the nucleus
or outside of the nucleus? Explain your reasoning.
11.
Isotope
31
18
P
O
Complete the chart below:
Atomic Number
Z
15
19
58
Ni
2+
Mass Number
A
39
58
Number of
Electrons
8
18
12. What is the mass (in grams) of
a. one 1H atom? ______________
b. one 12C atom? _____________
13. What is the mass (in grams) of 4.35 x 106 atoms of
12
C?
14. What is the mass (in grams) of one molecule of carbon dioxide
which has one 12C atom and two 16O atoms?
Adapted from Chemistry a Guided Inquiry and NCSSM Guided Inquiry
15. Define mass number
16. Define atomic number.
17. How many electrons, protons, and neutrons are found in each of
the following?
Atom or ion
Electrons
Protons
neutrons
24
Mg
23
Na+
35
Cl
35
Cl56
Fe3+
15
N
16 2O
27
Al3+
18. Estimate the mass of one 14C atoms (in amu) as precisely as you
can from the data given here. Explain your answer.
19. Use the data given to estimate the values (in amu) of
a. An electron
b. A proton
c. A neutron
20. The mass values calculated in #18 are only approximate because
when atoms (up through iron) are made (mainly in stars) from protons,
neutrons, and electrons, energy is released. Einstein’s equation E =
mc2 enables us to relate the energy released to the mass loss in the
formation of atoms. Use the known values for the mass of a proton,
1.0073 amu, mass of a neutron, 1.0087, and the mass of an electron,
5.486 x 10-4 amu, to show that the mass of a 12C atom is less than the
sum of the masses of the constituent particles.
Summary of Activity:
Describe an atom.
Adapted from Chemistry a Guided Inquiry and NCSSM Guided Inquiry