Matter Interactions Unit Test
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Question
Cobalt has a mass number of 59 and an atomic number of 27. A student wants to create a model of a cobalt atom. Which statement about the model is correct?(1 point)
Responses
The model should show 27 protons and 32 neutrons.
The model should show 27 protons and 32 neutrons.
The model should show 27 protons and 27 neutrons.
The model should show 27 protons and 27 neutrons.
The model should show 32 protons and 59 neutrons.
The model should show 32 protons and 59 neutrons.
The model should show 59 protons and 27 neutrons
The model should show 27 protons and 32 neutrons.
To determine the correct statement about the model of a cobalt atom, we need to understand the meaning of the mass number and atomic number. The atomic number represents the number of protons in an atom, while the mass number represents the total number of protons and neutrons.
In this case, the question states that cobalt has a mass number of 59 and an atomic number of 27.
Hence, the correct statement about the model of a cobalt atom is: "The model should show 27 protons and 32 neutrons."
The correct statement about the model is: The model should show 27 protons and 32 neutrons.
In a molecule of lithium sulfide, there are two atoms of lithium and one atom of sulfur. Which statement about lithium sulfide is correct?(1 point)
Responses
Both lithium and sulfur form positive ions.
Both lithium and sulfur form positive ions.
A molecular model of lithium sulfide would have two spheres.
A molecular model of lithium sulfide would have two spheres.
The atoms in lithium sulfide are held together by bonds.
The atoms in lithium sulfide are held together by bonds.
The chemical formula for lithium sulfide is LiS2.
The atoms in lithium sulfide are held together by bonds.
Which element has the same number of valence electrons as bromine (Br)?
(1 point)
Responses
chlorine (Cl)
chlorine (Cl)
potassium (K)
potassium (K)
krypton (Kr)
krypton (Kr)
selenium (Se)
chlorine (Cl)
Why are sodium (Na) and potassium (K) in the same group on the periodic table?(1 point)
Responses
They are both hard and brittle.
They are both hard and brittle.
They have similar atomic weights.
They have similar atomic weights.
They are both colorless.
They are both colorless.
They have similar reactivity.
They have similar reactivity.
A student cuts some fabric into two pieces. Is this change physical or chemical?(1 point)
Responses
It is a physical change because there is no reaction.
It is a physical change because there is no reaction.
It is a chemical change because there is no phase change.
It is a chemical change because there is no phase change.
It is a chemical change because the size changes.
It is a chemical change because the size changes.
It is a physical change because the process is reversible.