Atoms and Molecules Quiz
Questions: 16 · 10 minutes
1. A particle-level description says that every particle consists of two identical oxygen atoms bonded together. What does the sample contain?
Separate oxygen atoms
Molecules of a compound
Positively charged oxygen ions
Molecules of an element
2. Which subatomic particle determines which element an atom belongs to?
Neutron
Proton
Electron
Photon
3. A magnesium particle has 12 protons and 10 electrons. What is its overall charge?
A charge of negative two (2−)
No overall charge; it is neutral
A charge of positive ten (10+)
A charge of positive two (2+)
4. A neutral carbon atom has atomic number 6. How many electrons does it have?
12 electrons
6 electrons
3 electrons
8 electrons
5. A molecular model shows two hydrogen atoms bonded to one oxygen atom. Which formula represents it?
HO₂: one hydrogen and two oxygen atoms
H₂O₂: two hydrogen and two oxygen atoms
H₂O: two hydrogen and one oxygen atom
2HO: two separate one-to-one hydrogen–oxygen units
6. Which statement best defines a molecule?
A discrete group of two or more atoms held together by chemical bonds
A single atom that has gained or lost electrons
Any sample containing more than one element
The positively charged center of an atom
7. What type of bond holds the two oxygen atoms together in an O₂ molecule?
Ionic bond
Covalent bond
Hydrogen bond
Metallic bond
8. Two atoms are isotopes of the same element when they have:
Different numbers of protons and the same number of neutrons
The same mass number and different numbers of electrons
The same numbers of protons and neutrons but different charges
The same number of protons but different numbers of neutrons
9. A sample contains three CO₂ molecules. How many oxygen atoms are in the sample?
3 oxygen atoms
9 oxygen atoms
2 oxygen atoms
6 oxygen atoms
10. A methane molecule has the formula CH₄. Carbon has 6 protons, and each hydrogen atom has 1 proton. How many protons are in one methane molecule altogether?
10 protons
6 protons
8 protons
24 protons
11. A sealed container holds separate N₂ and O₂ molecules that have not reacted. How should its contents be classified?
A pure element
A single pure compound
A mixture of two elements
A mixture of two compounds
12. How many atoms are present in one molecule of H₂O?
4 atoms
2 atoms
3 atoms
1 atom
13. Why is oxygen gas, O₂, classified as an element rather than a compound?
It contains only one kind of atom
It can exist only as a gas
Each molecule contains exactly two atoms
Its atoms are not connected by a chemical bond
14. Complete the equation 2H₂ + O₂ → __H₂O so that the number of each type of atom is conserved. Which coefficient belongs in the blank?
Coefficient 1
Coefficient 2
Coefficient 3
Coefficient 4
15. What happens when a neutral sodium atom loses one electron?
It becomes a negatively charged ion
It becomes an isotope of sodium
It becomes a positively charged ion
It changes into a different element
16. How does one oxygen atom differ from one O₂ molecule?
An O₂ molecule contains two oxygen atoms chemically bonded together
An O₂ molecule contains one oxygen atom with two extra electrons
An oxygen atom is a compound, while O₂ is an element
An oxygen atom has no nucleus, while O₂ does