Free NEX Basic Chemistry: Atomic Structure and Chemical Reactions Questions and Answers 1 — Questions and Answers
Question 1: Which subatomic particle has a negative charge and orbits the nucleus of an atom?
- Proton
- Neutron
- Electron (Correct answer)
- Photon
Correct answer: Electron
Electrons are negatively charged particles that exist in shells or orbitals around the central nucleus. Protons are positive and neutrons are neutral, both located within the nucleus.
Question 2: The atomic number of an element is determined by the number of ___ in one atom of that element.
- neutrons
- electrons
- protons (Correct answer)
- ions
Correct answer: protons
The atomic number is the defining characteristic of an element. It is equal to the number of protons found in the nucleus of every atom of that element.
Question 3: In the chemical reaction Zn + 2HCl → ZnCl₂ + H₂, the products are:
- Zn and HCl
- ZnClâ‚‚ and Hâ‚‚ (Correct answer)
- Zn and ZnClâ‚‚
- HCl and Hâ‚‚
Correct answer: ZnClâ‚‚ and Hâ‚‚
In a chemical equation, the substances on the left side of the arrow are the reactants (what you start with). The substances on the right side of the arrow are the products (what is formed).
Question 4: Isotopes of an element are atoms that have the same number of protons but a different number of ___.
- electrons
- quarks
- neutrons (Correct answer)
- ions
Correct answer: neutrons
Isotopes are variants of a particular chemical element. While all isotopes of a given element have the same number of protons, they differ in the number of neutrons in their nuclei.
Question 5: The reaction 2H₂O → 2H₂ + O₂ is an example of which type of reaction?
- Synthesis
- Decomposition (Correct answer)
- Single displacement
- Combustion
Correct answer: Decomposition
A decomposition reaction is one in which a single compound breaks down into two or more simpler substances. Here, water (Hâ‚‚O) is breaking down into hydrogen (Hâ‚‚) and oxygen (Oâ‚‚).
Question 6: When the equation __N₂ + __H₂ → __NH₃ is balanced, what is the coefficient for H₂?
- 1
- 2
- 3 (Correct answer)
- 6
Correct answer: 3
To balance the equation, you need the same number of each type of atom on both sides. The balanced equation is N₂ + 3H₂ → 2NH₃, which gives 2 nitrogen atoms and 6 hydrogen atoms on each side.
Free NEX Basic Chemistry: Atomic Structure and Chemical Reactions Questions and Answers 1
Which subatomic particle has a negative charge and orbits the nucleus of an atom?