The duet rule or duplet rule of the first shell applies to H, He and Li—the noble gas helium has two electrons in its outer shell, which is very stable. (Since there is no 1p subshell, 1s is followed immediately by 2s, and thus shell 1 can only have at most 2 valence electrons).
What atoms are stable with 2 electrons?
Helium, the noble gas of the first row, has only two electrons. Hydrogen, the only element in the first row besides Helium, fulfills the “octet rule” by sharing two electrons only. Two hydrogen atoms form a covalent bond to make a hydrogen molecule.
How many electrons are stable?
Most of the elements important in biology need eight electrons in their outermost shell in order to be stable, and this rule of thumb is known as the octet rule. Some atoms can be stable with an octet even though their valence shell is the 3n shell, which can hold up to 18 electrons.
Is 2 valence electrons stable?
Helium in its valence shell can accommodate maximum two electrons only. That means it is completely filled. So it is very stable. On the other hand, in group 2 elements the valence shell is not half filled or completely filled so they are not stable.
How do you know if electrons are stable?
Atoms are at their most stable when their outermost energy level is either empty of electrons or filled with electrons. Sodium atoms have 11 electrons. Two of these are in the lowest energy level, eight are in the second energy level and then one electron is in the third energy level.
What makes an atom stable?
An atom is stable if the forces among the particles that makeup the nucleus are balanced. An atom is unstable (radioactive) if these forces are unbalanced; if the nucleus has an excess of internal energy. Instability of an atom’s nucleus may result from an excess of either neutrons or protons.
Why can there only be 2 electrons in the first shell?
This first shell has only one subshell (labeled 1s) and can hold a maximum of 2 electrons. This is why there are two elements in the first row of the periodic table (H & He). Because the first shell can only hold a maximum of 2 electrons, the third electron must go into the second shell.
How many electrons must an atom gain stability?
Atoms with greater stability have less energy, so a reaction that increases the stability of the atoms will release energy in the form of heat or light. A stable arrangement is attended when the atom is surrounded by eight electrons. This octet can be made up by own electrons and some electrons which are shared.
What is a stable electron configuration?
Stable configuration
Their valence shell is complete. They have two or eight electrons in their valence shell. They do not gain, lose or share electrons.
Which electron configuration is most stable?
A full valence shell is the most stable electron configuration.
How many valence electrons is the most stable?
Atoms with 8 electrons in their valence shell have completely filled last orbitals and are therefore the most stable, as their electronic configuration is similar to that of the closest noble gas.
How many valence electrons do stable ions have?
The octet rule states that an atom is most stable when there are eight electrons in its valence shell. Atoms with less than eight electrons tend to satisfy the duet rule, having two electrons in their valence shell. By satisfying the duet rule or the octet rule, ions are more stable.
Which of the following has valency 2?
It accepts two electrons from other atoms to complete its outermost shell. So, the two examples for the element with valency 2 are Magnesium and Oxygen.
What makes an atom unstable?
When the atoms of an element have extra neutrons or protons it creates extra energy in the nucleus and causes the atom to become unbalanced or unstable.
What makes a molecule stable?
If I say that a certain molecule is “stable”, I might mean any of a number of things: It’s possible to make it, and it won’t spontaneously fall apart. It’s possible to isolate a pure sample of the substance. It won’t react with other things.
How many stable electrons does oxygen have?
Thus, oxygen requires two electrons to achieve the electronic configuration similar to that of neon.
References:
- https://www.utdallas.edu/~scortes/ochem/OChem1_Lecture/Class_Materials/03_coval_bonding.pdf
- https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:atomic-structure-and-properties/x2eef969c74e0d802:atomic-structure-and-electron-configuration/a/the-periodic-table-electron-shells-and-orbitals-article
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