The octet rule also known as the rule of eight
In most cases it is the valance electrons which participate in chemical reactions. Transition state elements are a major exception; they undergo reactions that involve the inner electron shells as well.
Representative Elements
Element 17's valence electron configuration is 3s23p5.
The Bohr model of the atom places electrons in orbits or "shells." Elements in the first period only have electrons in the first shell. Elements in the second period have electrons in the first two shells. Elements in the third period have electrons in the first three shells, and so on.
That would be the Nobel gasses, 8A, because they have an octet of 8 electrons fully filling their valance shells so that they naturally do not react with other elements is either ionic or covalent bonding.
In most cases it is the valance electrons which participate in chemical reactions. Transition state elements are a major exception; they undergo reactions that involve the inner electron shells as well.
You should understand that while neutral atoms have the same number of protons and electrons, they do not usually have the same number of protons and valance electrons, because except for hydrogen and helium, atoms also have electrons in the inner shells, which are not valance electrons. Therefore, there is no atom which has 7 protons and 7 valance electrons, although there is an element that has 7 protons, and there are several elements that have 7 valence electrons.
You should understand that while neutral atoms have the same number of protons and electrons, they do not usually have the same number of protons and valance electrons, because except for hydrogen and helium, atoms also have electrons in the inner shells, which are not valance electrons. Therefore, there is no atom which has 7 protons and 7 valance electrons, although there is an element that has 7 protons, and there are several elements that have 7 valence electrons.
Representative Elements
The noble gasses. i ike men
Octet
Electronic shells: 2,8,18,32,25,8,2 Electronic cofiguration: [Rn]5f7.7s2 Oxidation states: 6,5,4,3
Element 17's valence electron configuration is 3s23p5.
The Bohr model of the atom places electrons in orbits or "shells." Elements in the first period only have electrons in the first shell. Elements in the second period have electrons in the first two shells. Elements in the third period have electrons in the first three shells, and so on.
That would be the Nobel gasses, 8A, because they have an octet of 8 electrons fully filling their valance shells so that they naturally do not react with other elements is either ionic or covalent bonding.
A group of elements that rarely combine with other elements because they already have eight electrons in the outer shells is a Noble Gas
Almost always, yes. This is why they are so stable and do not react: having filled valance shells, they can neither give up or gain an electron to become more stable. The exception to this rule are the heavier noble gases, whose outermost valance shells are more prone to ionization due to the shielding effect from the electrons in the lower valance shells.