Examples of 18 electron rule in the following topics:
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- The main body of the table is a 18 × 7 grid.
- Hydrogen has 1 electron in the 1s level, and to the right, helium, in Group 18, has 2 electrons in the 1s level, a completely filled shell, the duet rule.
- Across the period, first the 2s and then the 2p orbitals fill, arriving at the configuration for neon, following the octet rule.
- The electron shell configurations of the first 18 elements in the periodic table.
- Position in the periodic table based on electron shell configuration.
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- The Aufbau principle determines an atom's electron configuration by adding electrons to atomic orbitals following a defined set of rules.
- The order in which orbitals are filled is given by the Madelung rule.
- The rule is based on the total number of nodes in the atomic orbital, n + ℓ, which is related to the energy.
- In general, the Aufbau principle works very well for the ground states of the atoms for the first 18 elements, then decreasingly well for the following 100 elements.
- Order in which orbitals are arranged by increasing energy according to the Madelung Rule.
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- This movement of electrons from one element to another is referred to as electron transfer.
- As illustrated, sodium (Na) only has one electron in its outer electron shell.
- When sodium loses an electron, it will have 11 protons, 11 neutrons, and only 10 electrons.
- Therefore, it tends to gain an electron to create an ion with 17 protons, 17 neutrons, and 18 electrons.
- Both ions now satisfy the octet rule and have complete outer shells.
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- The innermost shell has a maximum of two electrons, but the next two electron shells can each have a maximum of eight electrons.
- This is known as the octet rule which states that, with the exception of the innermost shell, atoms are more stable energetically when they have eight electrons in their valence shell, the outermost electron shell.
- Theoretically, they would be more energetically stable if they followed the octet rule and had eight.
- As shown in , the group 18 atoms helium (He), neon (Ne), and argon (Ar) all have filled outer electron shells, making it unnecessary for them to gain or lose electrons to attain stability; they are highly stable as single atoms.
- Group 18 elements (helium, neon, and argon are shown) have a full outer, or valence, shell.
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- Lewis symbols (also known as Lewis dot diagrams or electron dot diagrams) are diagrams that represent the valence electrons of an atom.
- Lewis structures (also known as Lewis dot structures or electron dot structures) are diagrams that represent the valence electrons of atoms within a molecule.
- We say the electrons 'reside' in different principal energy levels, and these levels exist at different radii from the nucleus and have rules regarding how many electrons they can accommodate.
- The second principal energy level can have 8, the third can have 18, and so on, until all 79 electrons have been distributed.
- Notice that the outermost level has only one electron.
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- If an atom has the same number of protons and electrons, it is electronically neutral.
- The process is motivated by the achievement of more stable electronic configurations, such as the octet rule, which states that most stable atoms and ions have eight electrons in their outermost (valence) shell.
- Sodium has a +1 charge because sodium has eleven electrons.
- However, according to the octet rule, sodium would be more stable with 10 electrons (2 in its inner most shell, 8 in its outermost shell).
- Chlorine naturally has 17 electrons but it would be more stable with 18 electrons (2 in its inner most shell, 8 in its second shell, and 8 in its valence shell).
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- Main group elements in the third period and below form compounds that deviate from the octet rule by having more than 8 valence electrons.
- For the elements in the second period of the periodic table (principal energy level n=2), the s2p6 electrons comprise the octet, and no d sublevel exists.
- As a result, the second period elements (more specifically, the nonmetals C, N, O, F) obey the octet rule without exceptions.
- In the SF6 molecule, the central sulfur atom is bonded to six fluorine atoms, so sulfur has 12 bonding electrons around it.
- In the PCl5 molecule, the central phosphorus atom is bonded to five Cl atoms, thus having 10 bonding electrons and violating the octet rule.
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- For example, for boron through neon, the electron filling order of the 2p orbitals follows Hund's Rule.
- According to the first rule, electrons will always occupy an empty orbital before they pair up.
- For the second rule, unpaired electrons in singly occupied orbitals have the same spins.
- Hund's Rule also tells us that all of the unpaired electrons must have the same spin.
- Apply Hund's rule and justify its use to determine electron configurations for atoms in the ground state
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- An atom's electrons exist in discrete atomic orbitals, and the atom's electron configuration can be determined using a set of guidelines.
- This nucleus is surrounded by electrons.
- An atom's electron shell can accommodate 2n2 electrons, where n is the energy level.
- An element's electron configuration is the arrangement of the electrons in the shells.
- Electrons that occur together in an orbital are called an electron pair.
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- The total number of electrons represented in a Lewis structure is equal to the sum of the numbers of valence electrons in each individual atom.
- Non-valence electrons are not represented in Lewis structures.
- After the total number of available electrons has been determined, electrons must be placed into the structure.
- When counting electrons, negative ions should have extra electrons placed in their Lewis structures; positive ions should have fewer electrons than an uncharged molecule.
- The hypochlorite ion, ClO−, contains 13 + 1 = 14 electrons.