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Science 8 Unit 1 Test: Classification, Atomic Structure, Periodic Table

Grade 8 Unit 1 Summative Assessment

            📚 Science
                            🎓 Grade 8
                                        ⏱️ 45 minutes
                    

1
Unit Test

Question 1

What is an element?

One type of atom
Two or more types of atoms bonded in a fixed ratio
Two or more substances physically combined, no fixed ratio
A force that holds two or more atoms together as a unit

Question 2

What is a compound?

One type of atom
Two or more substances physically combined, no fixed ratio
Two or more types of atoms bonded in a fixed ratio
Matter made of only one type of particle throughout

Question 3

What is a mixture?

One type of atom throughout the whole sample
Two or more types of atoms bonded in a fixed ratio
Two or more substances physically combined, with no fixed ratio
A force that holds two or more atoms tightly together as a single chemical unit

Question 4

Which of these is classified as a pure substance?

Sugar water, a mixture of sugar and water
Sand mixed with iron filings, separable with a magnet
Oxygen gas (O2), an element
Ocean water, a mixture of water and dissolved salts

Question 5

Sugar dissolved in water looks uniform throughout. Why is sugar water still a mixture and not a compound?

Because sugar and water are both individually classified as pure elements
Because evaporating the water recovers the sugar unchanged, showing a physical change
Because sugar water is fully able to conduct an electric current
Because sugar water has one single, fixed, and completely unchanging chemical formula throughout

Question 6

Using the compound naming rule (metal name first, nonmetal second, nonmetal ending changed to -ide), what is the correct name for a compound of potassium and bromine?

Potassium bromine, simply joining the two element names together
Bromide potassium, the nonmetal placed before the metal
Potassium bromide, the metal first and nonmetal changed to -ide
Bromic potassium, using a different nonmetal ending

Question 7

Sand and iron filings can be separated with a magnet, but the sodium and chlorine in table salt cannot be pulled apart that way. What explains this difference?

Sand and iron filings are chemically bonded, while salt is not
Salt is a mixture whose parts blend together too well to separate
Sodium and chlorine bond into a new substance; sand and iron filings are only mixed
Iron filings are made of a naturally magnetic element, and salt is a magnetic compound too

Question 8

What is the nucleus of an atom?

The large, mostly empty region surrounding the nucleus where electrons are found
The small, dense region at the center of an atom, made of protons and neutrons
A subatomic particle carrying a negative electric charge
The outermost layer of electrons surrounding an atom

Question 9

What defines which element an atom is?

Its number of neutrons in the nucleus
Its number of electrons in the outer region
Its number of protons in the nucleus
Its total mass number, protons plus neutrons

Question 10

An atom has 12 protons and an atomic mass of about 24. About how many neutrons does it have?

24 neutrons, equal to the atomic mass
12 neutrons, the mass number minus the proton count
36 neutrons, adding the mass number and the proton count together
2 neutrons, the atomic mass divided by 12

Question 11

A neutral atom has 17 electrons. How many protons must it have?

8 protons, half of the electron count
17 protons, equal to the electron count
34 protons, double the electron count
0 protons, since electrons carry the charge instead

Question 12

Two atoms each have 8 protons. One has 8 neutrons and the other has 10 neutrons. Are they the same element?

No, because they have different numbers of neutrons
No, because they have different total mass numbers
Yes, because element identity depends only on proton count
Yes, but only if their electron counts also happen to match

Question 13

Where is almost all of an atom's mass located, and why?

In the electron region, since it takes up the most physical space
Spread evenly across the whole volume of the atom
In the nucleus, because protons and neutrons carry the mass, not electrons
In the electron region, because electrons are thought to be the single heaviest particle

Question 14

What charge does an electron carry?

A positive electric charge
A negative electric charge
No charge at all, like a neutron
A charge that changes depending on the element

Question 15

How is the periodic table organized?

Alphabetically, from Actinium to Zirconium
By the order in which each element was discovered
By atomic number, from lowest to highest
By how common each element is on Earth

Question 16

What do elements in the same group (column) of the periodic table share?

The exact same number of protons found in the nucleus of the atom
Similar properties and similar chemical reactivity
The exact same atomic mass, element to element
The exact same color and physical texture

Question 17

Silicon (Si) sits directly on the staircase line of the periodic table. What kind of element is it?

A metal, sitting to the left of the staircase
A nonmetal, sitting to the right of the staircase
A metalloid, sitting directly on the staircase
A noble gas, found in the rightmost column

Question 18

An element has a completely full outer electron shell. What does this predict about its reactivity and which group it belongs to?

Highly reactive, most likely an alkali metal
Unreactive, most likely a noble gas
Highly reactive, most likely a halogen
Unreactive, most likely a transition metal

Question 19

An element has only one valence electron in its outer shell. What does the valence rule predict?

It is unreactive, most likely a noble gas
It is highly reactive, most likely an alkali metal
It is a metalloid sitting on the staircase
It has no electrons at all anywhere in its entire outer shell

Question 20

How many total atoms make up one molecule of CO2, and what are they?

2 atoms total: 1 carbon and 1 oxygen
3 atoms total: 1 carbon and 2 oxygen
3 atoms total: 2 carbon and 1 oxygen
4 atoms total: 2 carbon and 2 oxygen

Question 21

This group has a completely full outer electron shell, making its elements unreactive. Which grouping is this?

Noble Gases
Alkali Metals
Metalloids
Transition Metals
Halogens

Question 22

This group has just one valence electron, making its elements highly reactive metals. Which grouping is this?

Noble Gases
Alkali Metals
Metalloids
Transition Metals
Halogens

Question 23

This group sits on the staircase line, showing some properties of metals and some of nonmetals. Which grouping is this?

Noble Gases
Alkali Metals
Metalloids
Transition Metals
Halogens

Question 24

This group of elements fills the large central block of columns between the alkaline earth metals and the post-transition metals. Which grouping is this?

Noble Gases
Alkali Metals
Metalloids
Transition Metals
Halogens

Question 25

This group of highly reactive nonmetals sits just one column to the left of the noble gases. Which grouping is this?

Noble Gases
Alkali Metals
Metalloids
Transition Metals
Halogens

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