Name : __________________ Science- 8 Period __________ Date: _______________________
Chemistry Unit Review
1. The atomic number for Phosphorous is 15. What does this tell you about Phosphorous?
Has 15 protons
Has 15 electrons
2. What is the number of neutrons in a neutral atom of Rubidium?
48
3. Describe the most reactive and least reactive families of the Periodic Table of Elements.
Group 1 (hydrogen family) is the most reactive because they have only 1 valence
electron it wants to give up really bad
Group 18 (helium family; Noble Gases) is least reactive because they have 8
valence electrons making its outer shell full…they do not want more or to give up
any
4. How many valence electrons exist in an electrically neutral atom of Aluminum? What does this
tell you about the Boron Family that contains Aluminum?
3
Everyone contains 3 valence electrons and will react in similar ways
5. Describe possible evidence that would suggest that a chemical change has occurred?
(max 3 checks)
change in color
light given off
temperature change
new substance formed
gas given off
bubbles
smell given off
precipitate
6. How many protons are in one molecule of NH4? How many protons would there be in two
molecules of NH4?
(7+1+1+1+1) 11
2 x 11 = 22
7. Describe the chemical formula: 4NaHCO3.
4 molecules of a compound containing 1 atom of sodium, 1 atom of hydrogen, 1
atom of carbon, and 3 atoms of oxygen
8. List and describe the 3 subatomic particles of an atom. Include location, mass, and charge.
Proton: + charge; mass = 1 amu; nucleus
Neutron: no charge; mass = 1 amu; nucleus
Electron: - charge, mass ≈ 0; electron cloud
9. Name 3 elements that have similar chemical properties to Cesium.
Hydrogen
Lithium
Sodium (or potassium,
rubidium, francium)
10. Explain why a chemical equation must be balanced.
Law of Conservation of Matter (Mass) – matter cannot be created nor destroyed,
just rearranged
11. What are the reactants in the following chemical equation:
O2 + C6H12O6
CO2 + H2O + energy
Oxygen (O2)
Sugar (C6H12O6)
12. How many atoms are in one molecule of C6H12O6?
24
13. Describe a chemical formula? Why is a chemical formula used in Science?
Way to express a compound using element symbols
Short, easy way to show complicated reactions
14. Define the following words: atom, element, molecule, compound.
Atom: smallest particle of an element; cannot be broken down by physical or
chemical means
Element: substance made up of only 1 type of atom
Molecule: 2 or more
ATOMS
Compound: 2 or more
that are chemically combined
ELEMENTS
that are chemically combined
15. Is the following chemical equation balanced: 6O2 + C6H12O6
3CO2 + 4H2O?
No: oxygen, carbon, and hydrogen are not equal on both sides of the equation
16. List the following information about Potassium: atomic number, symbol, atomic mass, number of
protons, number of electrons, number of neutrons, number of valence electrons, the group
number, and the period number.
#: 19
P+: 19
Ve-: 1
Sym: K
e-: 19
Grp: 1
Mass: 39
N0: 20
Per: 4
17. Draw a Bohr model of the element Silicon.
18.
14 P+
14 N0
DEFINITIONS:
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Atom - smallest particle of an element; cannot be broken down by physical or chemical
means
atomic mass – sum of the # of protons and neutrons found in the nucleus of an atom
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atomic number – identifies the element by expressing the number of protons in it
Bohr model – diagram of an atom of an element showing the protons & neutrons in the
nucleus, the number of electron orbitals and number of electrons in each orbital
Compound - 2 or more ELEMENTS that are chemically combined
Electron – negatively charged subatomic particle with a mass of about 0 orbiting the
nucleus of an atom (in the electron cloud)
electron cloud – area (zone) where electrons are found orbiting the nucleus of an atom
element - substance made up of only 1 type of atom
molecule - 2 or more ATOMS that are chemically combined
neutron – subatomic particle with no charge (neutral) & having a mass of 1 amu which is
located in the nucleus of an atom
nucleus – central portion of an atom containing protons and neutrons
products – the resulting substance(s) made from a chemical reaction
proton – located in the nucleus, it is a positively charged particle with a mass of 1 amu
reactants – those substances that interact in a chemical reaction to form new substances
valence electrons – the electrons located in the outer most orbital of an atom that are
used (shared) in chemical reactions to bond elements
60 Possible checks
CKS GRD
60 100
59 98
58 97
57 95
56 93
55 92
54 90
53 88
52 87
51 85
50 83
49 82
48 80
47 78
46 77
CKS GRD
45 75
44 73
43 72
42 70
41 68
40 67
39 65
38 63
37 62
36 60
35 58
34 57
33 55
32 53
31 52
CKS GRD
30 50
29 48
28 47
27 45
26 43
25 42
24 40
23 38
22 37
21 35
20 33
19 32
18 30
17 28
16 27
CKS GRD
15 25
14 23
13 22
12 20
11 18
10 17
9
15
8
13
7
12
6
10
5
8
4
7
3
5
2
3
1
2