Electron Shells, Valency and Atomic Number

Name: Electron Shells, Valency and Atomic Number
Author: StemPy Lab

Electrons sit in shells, and the outer shell decides how an atom behaves. Here we learn the rules for filling the shells, how to find the valency of an atom, and how the atomic number and the mass number tell us the particles in an atom.

3 lessons, about 1 h 15 min3 simulations10 problems6 practice questionsPython in every lesson

Created by StemPy Lab

Course outline (3 lessons)

Lesson 1about 25 min
Filling the shells
The most electrons that shell number n can hold is 2n². The outermost shell holds at most 8, and the shells fill from the inside, one after the other.
1 simulation2 practice questions1 Python program4 problems1 Python lab
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Lesson 2about 25 min
Valency and the outer shell
The electrons in the outer shell are valence electrons. An atom with a full outer shell is stable and its valency is zero. Other atoms gain, lose or share electrons to get a full outer shell, and the number they use is the valency.
1 simulation2 practice questions1 Python program3 problems1 Python lab1 question set
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Lesson 3about 25 min
Atomic number and mass number
The atomic number Z is the number of protons in the nucleus, and it identifies the element. The mass number A is the number of protons plus neutrons, so the number of neutrons is A minus Z. In a neutral atom the number of electrons is equal to the number of protons. An ion has the same protons and neutrons as its atom and a different number of electrons. An atom is written with the mass number at the top left and the atomic number at the bottom left of its symbol.
1 simulation2 practice questions1 Python program3 problems1 note
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Test Your Learning

Shells, Valency and Numbers: Challenge Paper

10 questions · 20 min

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More onStructure of the Atom › Electronic Configuration and Valency Structure of the Atom › Isotopes and Isobars

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Electron Shells, Valency and Atomic Number

Course outline (3 lessons)

Filling the shells

Valency and the outer shell

Atomic number and mass number

Test Your Learning

Your teacher

Discussion (0)