Multiple Choice
Which element on the periodic table has 25 protons?
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2. Atoms & Elements
Periodic Table: Element Symbols
Multiple Choice
Which of the following lists contains only correct chemical symbols for three different atoms or atomic cations with electrons?
A
C, O2+, H2
B
He, Br-, K2
C
Na, Cl, Fe
D
N, Ca+, Xe
Verified step by step guidance1
Step 1: Understand that chemical symbols represent elements and their ions. A correct chemical symbol consists of the element's one- or two-letter symbol, with the first letter capitalized and the second letter (if any) lowercase. If the species is an ion, the charge is indicated as a superscript (e.g., 2+, 3-).
Step 2: Analyze each list to check if the symbols are valid and represent different atoms or atomic cations with electrons. For example, 'C' is carbon, 'O2+' means an oxygen ion with a 2+ charge, and 'H2' is a molecule, not an atom or atomic cation, so 'H2' is not a correct atomic symbol.
Step 3: Check the second list: 'He' is helium, 'Br-' is a bromide ion (correct), but 'K2' suggests a diatomic potassium molecule, which is not a standard atomic symbol or ion, so 'K2' is incorrect.
Step 4: The third list 'Na, Cl, Fe' contains sodium (Na), chlorine (Cl), and iron (Fe), all valid atomic symbols for different atoms or atomic cations (if charged). This list is correct.
Step 5: The fourth list 'N, Ca+, Xe' includes nitrogen (N), calcium ion with a positive charge (Ca+), and xenon (Xe), all valid symbols for different atoms or atomic cations. This list is also correct.
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