This is the real Level 1 question set — 20 questions, free, no account needed.
Tap a question to check your answer and read the explanation.
1. An atom has atomic number 17 and mass number 35. How many neutrons does it contain?
A. 17
B. 18
C. 35
D. 52
Explanation: Number of neutrons = mass number - atomic number = 35 - 17 = 18.
2. A salt solution turns blue litmus red. The solution is ___.
A. basic
B. neutral
C. acidic
D. a buffer
Explanation: Acids turn blue litmus red.
3. The atomic number of an element represents the number of
A. neutrons in the nucleus
B. protons in the nucleus
C. electrons and neutrons combined
D. electron shells
Explanation: The atomic number of an element is defined as the number of protons found in the nucleus of an atom of that element.
4. A covalent bond is best described as a bond formed by the
A. transfer of electrons from one atom to another
B. sharing of a pair of electrons between two atoms
C. attraction between free electrons and metal cations
D. loss of protons from an atom
Explanation: A covalent bond is formed when two atoms share a pair of electrons, usually between non-metal atoms.
5. An element X has atomic number 12. What is the electron configuration of X?
A. 2,8,2
B. 2,8,1
C. 2,10
D. 2,8,3
Explanation: With atomic number 12, X has 12 electrons. Filling shells: 2 in the first shell, 8 in the second shell, and 2 in the third shell, giving 2,8,2.
6. The particle with a negative charge in an atom is the ___.
A. proton
B. neutron
C. electron
D. nucleus
Explanation: Electrons carry a negative charge and orbit the nucleus.
7. An element in Group 2 of the periodic table, such as magnesium, typically has a valency of
A. 1
B. 2
C. 3
D. 4
Explanation: Elements in Group 2 have two electrons in their outermost shell, which they tend to lose, giving them a valency of 2.
8. A dative (coordinate) covalent bond differs from a normal covalent bond because
A. electrons are transferred completely from one atom to another
B. both electrons in the shared pair come from only one of the bonding atoms
C. it only occurs between two metal atoms
D. no electrons are involved in the bond
Explanation: In a dative bond, one atom donates both electrons of the shared pair, unlike a normal covalent bond where each atom contributes one electron.
9. Common table salt used in Nigerian kitchens, sodium chloride, is held together mainly by which type of bond?
A. Covalent bond
B. Metallic bond
C. Ionic bond
D. Hydrogen bond
Explanation: Sodium chloride is formed by the electrostatic attraction between the Na+ cation and Cl- anion, which is an ionic bond.
10. What is the maximum number of electrons that can occupy the second (K+1) shell, that is, the L shell, of an atom?
A. 2
B. 8
C. 18
D. 32
Explanation: The maximum number of electrons in a shell is given by 2n^2, where n is the shell number. For the second shell (n=2), 2(2)^2 = 8.
11. Which pair of elements is most likely to combine through ionic bonding?
A. Chlorine and chlorine
B. Sodium and chlorine
C. Hydrogen and oxygen
D. Carbon and hydrogen
Explanation: Ionic bonding typically occurs between a metal (sodium) and a non-metal (chlorine), where electrons are transferred from the metal to the non-metal.
12. According to the octet rule, atoms are generally most stable when their outermost shell contains how many electrons?
A. 2
B. 6
C. 8
D. 10
Explanation: The octet rule states that atoms tend to gain, lose, or share electrons to attain eight electrons in their outermost shell, similar to noble gases (except helium, which is stable with 2).
13. Isotopes of an element have the same number of ___ but different numbers of neutrons.
A. electrons only
B. protons
C. nucleons
D. ions
Explanation: Isotopes share the same atomic number (protons) but differ in mass number.
14. Which is a physical change?
A. burning of wood
B. rusting of iron
C. melting of candle wax
D. souring of milk
Explanation: Melting changes state only; no new substance forms.
15. Metals such as the copper used in electrical wiring conduct electricity well because they contain
A. delocalized (free-moving) electrons
B. only covalent bonds
C. no electrons at all
D. fixed ions with no charge
Explanation: In metals, valence electrons are delocalized and free to move throughout the metallic structure, allowing metals like copper to conduct electricity.
16. Which of the following subatomic particles has a negative charge?
A. Proton
B. Neutron
C. Electron
D. Nucleon
Explanation: The electron carries a negative charge, the proton carries a positive charge, while the neutron is neutral. Nucleon is a general term for protons and neutrons found in the nucleus.
17. Isotopes of an element are atoms that have the same number of protons but different numbers of which particle?
A. Electrons
B. Neutrons
C. Protons
D. Nucleons in the shell
Explanation: Isotopes have the same atomic number (protons) but differ in the number of neutrons, which changes their mass number.
18. Noble gases such as argon are generally unreactive because their atoms have
A. an incomplete outer shell
B. a complete (full) outer electron shell
C. a very large number of protons
D. no electrons at all
Explanation: Noble gases have a full outer shell of electrons, making them very stable and largely unreactive.
19. Elements in the same group of the periodic table have similar chemical properties mainly because they have the same
A. number of neutrons
B. number of electron shells
C. number of electrons in the outermost shell
D. atomic mass
Explanation: Elements in the same group have the same number of valence (outermost shell) electrons, which determines their chemical behaviour.
20. In a neutral atom, the number of electrons is always equal to the number of which particle?
A. Neutrons
B. Protons
C. Nucleons
D. Isotopic mass
Explanation: A neutral atom has no overall charge, so the number of negatively charged electrons must equal the number of positively charged protons.
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