This atomic structure worksheet provides comprehensive practice on subatomic particles, isotopes, and the history of atomic theory for chemistry students.

Let's solve each question on the Chemistry Atomic Structure Worksheet step by step, based on the information provided and fundamental chemistry concepts.

---

Question 1: Analyzing the atomic structure diagram

The diagram shows:
- 11 protons (p⁺) in the nucleus
- 12 neutrons (n⁰) in the nucleus
- Electrons arranged in shells: 2 in the first shell, 8 in the second, and 1 in the third

#### i) Which element is the atom shown above?

The number of protons (atomic number) determines the element.
Here, 11 protons → Atomic number = 11, which corresponds to Sodium.

✔ Answer: Sodium

#### ii) What is the chemical symbol of the element?

The chemical symbol for sodium is Na.

✔ Answer: Na

#### iii) What is the mass of the atom shown above?

Mass number = protons + neutrons
= 11 + 12 = 23

So, this is Sodium-23.

✔ Answer: 23

#### iv) How many valence electrons are shown in the atom above?

Valence electrons are the electrons in the outermost shell.
From the diagram: The third shell has 1 electron.

✔ Answer: 1

---

Question 2: Which subatomic particle did J.J. Thomson discover?

J.J. Thomson discovered the electron through his cathode ray experiments, leading to the "plum pudding" model.

✔ Answer: Electron

---

Question 3: The nucleus was discovered by which scientist?

Ernest Rutherford discovered the nucleus through his gold foil experiment.

✔ Answer: c) Rutherford

---

Question 4: What is the mass of Carbon-14?

Carbon-14 means the mass number is 14.
So, the mass of the atom is approximately 14 atomic mass units (amu).

✔ Answer: 14 amu

---

Question 5: What is the number of protons in Carbon-14?

All carbon atoms have 6 protons (atomic number of carbon is 6).

✔ Answer: 6

---

Question 6: What is the number of neutrons in Carbon-14?

Neutrons = Mass number – Protons
= 14 – 6 = 8

✔ Answer: 8

---

Question 7: What is the number of protons in Uranium-238?

Uranium has an atomic number of 92, so it has 92 protons.

✔ Answer: 92

---

Question 8: What is the number of neutrons in Sulfur-33?

Sulfur has atomic number 16 → 16 protons
Neutrons = 33 – 16 = 17

✔ Answer: 17

---

Question 9: Neutral atoms of the same element can differ in

Neutral atoms of the same element have the same number of protons and electrons.
But they can differ in number of neutrons, which changes the mass number.

This leads to isotopes.

So, they can differ in mass number.

✔ Answer: a) Mass number

---

Question 10: The basic principles of atomic theory were first conceived by

John Dalton proposed the first modern atomic theory in the early 1800s.

✔ Answer: c) Dalton

---

✔ Final Answers:

1.
i) Sodium
ii) Na
iii) 23
iv) 1

2. Electron
3. c) Rutherford
4. 14 amu
5. 6
6. 8
7. 92
8. 17
9. a) Mass number
10. c) Dalton

---

Let me know if you'd like this formatted as a completed worksheet!