Which term correctly completes the sentence: 'I can't list every ___ on the periodic table, but I know a few, like oxygen, mercury, and lead!'?

• A. element symbol
• B. isotope
• C. atomic number
• D. period

Answer: (A)

Verified step by step guidance

1. Understand the sentence context: It talks about naming a few items on the periodic table, such as oxygen, mercury, and lead.
2. Recall that the periodic table is organized by elements, each having a unique name and a unique symbol (like O for oxygen, Hg for mercury, Pb for lead).
3. Consider the options: 'element symbol' refers to the one- or two-letter abbreviation for an element; 'isotope' refers to atoms of the same element with different numbers of neutrons; 'atomic number' is the number of protons in an element; 'period' refers to the horizontal rows in the periodic table.
4. Since the sentence says 'I can't list every ___ on the periodic table, but I know a few, like oxygen, mercury, and lead,' it implies naming the elements themselves or their symbols, not numbers or rows.
5. Therefore, the term that best fits the blank is 'element symbol' because it directly relates to naming specific elements on the periodic table.