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Atomic Theory Review Sheet
Complete the following chart..
PARTICLE
proton
neutron
electron
CHARGE
Positive
Neutral
Negative
MASS
1 amu
1 amu
0 amu
LOCATION
Nucleus
Nucleus
Outside of the nucleus
Define the following terms:
1. Atom – the smallest part of an element that still retains the properties of that element
2. Isotope – occurs when atoms of the same element have a different number of neutrons
3. Atomic number – determines the identity of an element, number of protons & electrons
4. Mass number – the total number of protons and neutrons in the nucleus of an atom
Short Answer:
5. What is the charge of an atom and why?
Atoms are neutral because the positive protons cancel the negative electrons.
6. Summarize the main concepts of Dalton’s Atomic Theory.
1. All elements are composed of tiny indivisible particles called atoms.
2. Atoms of the same element are identical AND atoms of different elements are different
3. Atoms of different elements can physically mix together or combine in simple whole
number ratios.
4. Chemical reactions occur when atoms are separated, joined or rearranged, but atoms of
one element are never changed into another element as a result of a reaction.
7. Which parts of Dalton’s theory are no longer accepted and why?
divisible AND 2. atoms of the same element are identical
1. Atoms are now known to be
8. Experiments with a cathode ray tube led to the discovery of the _____electron____.
9. Explain how Rutherford’s gold foil experiment worked, and what it proved.
Rutherford shot radioactive particles through gold foil onto photo paper. He expected all the
particles to go straight through, but some bounced back. This told him that there was a
positively charged, very dense center called the nucleus.
10. What determines the identity of an atom?
The atomic number or number of protons identifies it.
11. Define the law of definite proportions.
States that any sample of a compound always has the same composition.
12. Define the law of multiple proportions.
States that elements always combine in simple whole number increments; ex) H2O & H2O2
13. Define the law of conservation of mass.
States that mass can’t be created or destroyed; mass of reactants is EQUAL to mass of the reactants
14. What do isotopes of the same element have in common and what is different?
Isotopes have the same atomic number, # of protons & # of electrons.
Isotopes have different mass numbers and # of neutrons.
15. An element has 19 protons, 19 electrons and 20 neutrons. It has an atomic number of __19_ and a
mass number of __39__? What is the identity of this element?___potassium_____
16. An element has 8 protons, 8 electrons and 8 neutrons. It has an atomic number of __8_ and a mass
number of __16__? What is the identity of this element? _____oxygen_____
17. What is the number of protons, neutrons and electrons for:
Chlorine-35 17 protons, 18 neutrons, 17 electrons
Argon-40
18 protons, 22 neutrons, 18 electrons
67
30
Zn
28
14
Si
30 protons, 37 neutrons, 30 electrons
14 protons, 14 neutrons, 14 electrons
18. If Chlorine-35 has 18 neutrons, how many electrons does it have? 17 electrons
19. How do you find the following:
A. Number of protons in an atom = atomic number
B. Number of neutrons in an atom = mass # – atomic #
C. Number of electrons in an atom = atomic number (same as protons)
Symbol
C
Br
P
F
Zn
Atomic
Number
6
35
15
9
30
Mass
Number
14
80
31
19
95
Number of
Protons
6
35
15
9
30
Number of
Electrons
6
35
15
9
30
Number of
Neutrons
8
45
16
10
65