Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

2. Cell Chemistry & Cell Components

Atoms- Smallest Unit of Matter

Anatomy & Physiology

2. Cell Chemistry & Cell Components

Atoms- Smallest Unit of Matter

Previous problemNext problem

1:39 minutes

Problem 30

Textbook Question

An atom of the element calcium has 20 protons and 20 neutrons. Determine the following information about calcium:
(a) Number of electrons
(b) Atomic number
(c) Atomic weight
(d) Number of electrons in each energy level

Verified step by step guidance

Step 1: Determine the number of electrons in a neutral atom of calcium. Since calcium is neutral, the number of electrons equals the number of protons, which is 20.

Step 2: Identify the atomic number of calcium. The atomic number is defined as the number of protons in the nucleus of an atom. For calcium, this is 20.

Step 3: Calculate the atomic weight of calcium. The atomic weight is approximately the sum of the protons and neutrons in the nucleus. For calcium, this is 20 protons + 20 neutrons = 40 atomic mass units (amu).

Step 4: Determine the distribution of electrons in each energy level. Calcium has 20 electrons, which are distributed across energy levels as follows: the first energy level holds 2 electrons, the second holds 8 electrons, the third holds 8 electrons, and the fourth holds the remaining 2 electrons.

Step 5: Review the periodic table to confirm the electron configuration and atomic properties of calcium. Calcium is in Group 2 (alkaline earth metals) and Period 4, which aligns with its electron configuration and atomic structure.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Atomic Structure

An atom consists of protons, neutrons, and electrons. Protons and neutrons are located in the nucleus, while electrons orbit around the nucleus in energy levels. The number of protons defines the element, while the number of neutrons contributes to the atomic mass.

Atomic Number

The atomic number is the number of protons in an atom's nucleus and uniquely identifies an element. For calcium, the atomic number is 20, which means it has 20 protons. This number also indicates the number of electrons in a neutral atom, balancing the positive charge of protons.

Atomic Weight

Atomic weight is the weighted average mass of an element's isotopes, measured in atomic mass units (amu). For calcium, the atomic weight is approximately 40.08 amu, reflecting the sum of protons and neutrons in the nucleus. It is important for understanding the mass of atoms in chemical reactions.