Arrange the following elements in terms of their atomic number from lowest to highest:
- Carbon
- Oxygen
- Sodium
- Silicon
Show Answer & Explanation
Correct Answer: (D)
Explanation:
The atomic number (number of protons) for each element is:
- (1) Carbon (C): 6
- (2) Oxygen (O): 8
- (3) Sodium (Na): 11
- (4) Silicon (Si): 14
Arranging these atomic numbers from lowest to highest gives 6, 8, 11, and 14. This corresponds to the sequence (1), (2), (3), (4).
📚 Additional Info: Element Properties
For prelims exams, it is useful to know the atomic numbers for at least the first 20 elements, as well as their basic classification.
| Element | Symbol | Atomic Number (Z) | Period / Group | Classification |
|---|---|---|---|---|
| (1) Carbon | C | 6 | Period 2 / Group 14 | Nonmetal |
| (2) Oxygen | O | 8 | Period 2 / Group 16 | Nonmetal |
| (3) Sodium | Na | 11 | Period 3 / Group 1 | Alkali Metal |
| (4) Silicon | Si | 14 | Period 3 / Group 14 | Metalloid |
Key Exam Concepts
- Atomic Number (Z): The number of protons in an atom’s nucleus. It defines the element.
- Mass Number (A): The total number of protons and neutrons.
- Period: The horizontal rows in the periodic table. Elements in the same period have the same number of electron shells. (e.g., Sodium and Silicon are both in Period 3).
- Group: The vertical columns. Elements in the same group have the same number of valence electrons and thus similar chemical properties.
- Metalloid: An element (like Silicon) that has properties intermediate between metals and nonmetals. They are important as semiconductors.