Textbook Question
The subatomic particle with the least mass
(a) Carries a negative charge
(b) Carries a positive charge
(c) Plays no part in the atom's chemical reactions
(d) Is found only in the nucleus
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2. Cell Chemistry & Cell Components
Atoms- Smallest Unit of Matter
1:39 minutesProblem 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 guidance1
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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Video duration:
1mKey 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 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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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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