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?
The model should
O show 32 protons and 59 neutrons.
The model should
O show 59 protons and 27 neutrons.
The model should
O show 27 protons and 27 neutrons.
The model should
O show 27 protons and 32 neutrons.
The correct statement 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?
The chemical
• formula for lithium sulfide is LiS2.
A molecular model
O Of lithium sulfide
would have two spheres.
Both lithium and
• sulfur form positive
ions.
The atoms in lithium
O sulfide are held
together by bonds.
The correct statement is: The atoms in lithium sulfide are held together by bonds.
Which element has the same
number of valence electrons as
bromine (Br)?
(1 point)
• chlorine (CI)
• selenium (Se)
O potassium (K)
• krypton (Kr)
The element that has the same number of valence electrons as bromine (Br) is chlorine (CI).
You sure?
Apologies for the incorrect response. Bromine (Br) belongs to Group 17 or Group VIIA of the periodic table, which means it has 7 valence electrons. Therefore, the element that has the same number of valence electrons as bromine is chlorine (Cl).
Why are sodium (Na) and potassium (K) in the same group on the periodic table? (1 point)
O They have similar
atomic weights.
O They have similar
reactivity.
o They are both hard
and brittle.
o They are both
colorless.
The correct answer is: They have similar reactivity. Sodium (Na) and potassium (K) are both alkali metals and belong to Group 1 or Group IA of the periodic table. Elements in the same group tend to have similar chemical properties, including reactivity. Sodium and potassium both have one valence electron and react similarly to form ionic compounds and gain a stable electron configuration.
A student cuts some fabric into two pieces. Is this change physical or chemical? (1 point)
It is a physical
O change because
there is no reaction.
It is a chemical o change because there is no phase change.
It is a physical o change because the process is reversible.
It is a chemical
• change because the size changes.