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Ch. 2 The Chemical Level of Organization
Martini - Fundamentals of Anatomy and Physiology 12th Edition
Martini, Nath, Bartholomew12th EditionFundamentals of Anatomy and PhysiologyISBN: 9780137854011Not the one you use?Change textbook
All textbooksMartini, Nath, Bartholomew 12th EditionCh. 2 The Chemical Level of OrganizationProblem 30
Chapter 2, Problem 30

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
1
Identify the number of electrons in a neutral calcium atom. Since the atom has 20 protons and is neutral, the number of electrons equals the number of protons, which is 20.
Determine the atomic number of calcium. The atomic number is defined as the number of protons in the nucleus of an atom, so for calcium, it is 20.
Calculate the atomic weight (mass number) of calcium. This is the sum of protons and neutrons in the nucleus, so add 20 protons and 20 neutrons to get the atomic weight.
Understand the distribution of electrons in energy levels (shells). Electrons fill shells in a specific order based on their capacity: the first shell holds up to 2 electrons, the second up to 8, the third up to 18, and so on.
Assign the 20 electrons of calcium to the energy levels following the order of filling: place 2 electrons in the first shell, 8 in the second shell, and the remaining electrons in the third and possibly fourth shells according to their maximum capacities.

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Key Concepts

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

Atomic Number

The atomic number is the number of protons in an atom's nucleus. It uniquely identifies an element and determines its position on the periodic table. For calcium, the atomic number is 20, meaning it has 20 protons.
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Atomic Properties

Atomic Weight (Mass Number)

Atomic weight, often called mass number, is the total number of protons and neutrons in an atom's nucleus. It represents the atom's mass relative to other atoms. For calcium with 20 protons and 20 neutrons, the atomic weight is 40.
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Atomic Properties

Electron Configuration and Energy Levels

Electron configuration describes how electrons are arranged in an atom's energy levels or shells. Calcium has 20 electrons distributed across energy levels following the 2, 8, 8, 2 pattern, filling shells from the innermost to outermost.
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Introduction to Energy
Related Practice
Textbook Question

In an exergonic reaction,

(a) Large molecules are broken down into smaller ones.

(b) Small molecules are assembled into larger ones.

(c) Molecules are rearranged to form new molecules.

(d) Molecules move from reactants to products and back.

(e) Energy is released during the reaction.

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Textbook Question

A certain reaction pathway consists of four steps. How would decreasing the amount of enzyme that catalyzes the second step affect the amount of product produced at the end of the pathway?

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Textbook Question

The hydrogen bonding that occurs in water is responsible for all of the following except

(a) The high boiling point of water

(b) The low freezing point of water

(c) The ability of water to dissolve nonpolar substances

(d) The ability of water to dissolve inorganic salts

(e) The surface tension of water

Textbook Question

A sample that contains an organic molecule has the following constituents: carbon, hydrogen, oxygen, nitrogen, and phosphorus. Is the molecule more likely to be a carbohydrate, a lipid, a protein, or a nucleic acid?

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Textbook Question

An important buffer system in the human body involves carbon dioxide (CO₂) and bicarbonate ion (HCO₃-) in the reversible reaction

CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃-

If a person becomes excited and exhales large amounts of CO2, how will the pH of the person's body be affected?

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