<u>Answer:</u> The given isotope of tin has 50 protons and 69 neutrons.
<u>Explanation:</u>
Atomic number is defined as the number of protons or number of electrons that are present in neutral atom. It is represented as Z.
Atomic number = Number of protons = Number of electrons
Mass number is defined as the sum of number of protons and number of neutrons. It is represented as A.
Mass number = Number of protons + Number of neutrons
We are given:
An isotope having representation 
Mass number of Sn = 19
Atomic number = 50
Number of neutrons = Mass number - Atomic number = 119 - 50 = 69
Hence, the given isotope of tin has 50 protons and 69 neutrons.
What are the answer choices?
Answer:
0.206 mol H₂O₂
General Formulas and Concepts:
<u>Chemistry - Atomic Structure</u>
- Reading a Periodic Table
- Using Dimensional Analysis
Explanation:
<u>Step 1: Define</u>
7.00 moles H₂O₂
<u>Step 2: Identify Conversions</u>
Molar Mass of H - 1.01 g/mol
Molar Mass of O - 16.00 g/mol
Molar Mass of H₂O₂ - 2(1.01) + 2(16.00) = 34.02 g/mol
<u>Step 3: Convert</u>
<u />
= 0.205761 mol H₂O₂
<u>Step 4: Check</u>
<em>We are given 3 sig figs. Follow sig fig rules and round.</em>
0.205761 mol H₂O₂ ≈ 0.206 mol H₂O₂