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How is the valency of an element determined when the outermost shell is nearly full?
By the total number of neutrons in the nucleus
By the total number of protons in the nucleus
By the total mass of the atom
By the number of electrons needed to complete the octet
By the number of electrons needed to complete the octet
The valency of an element is determined by its tendency to achieve a stable electronic configuration, typically an octet (eight electrons) in the outermost shell. If the outermost shell is nearly full, the atom gains the necessary number of electrons to complete its octet, and this number defines its valency.
The valency of an element is determined by its tendency to achieve a stable electronic configuration, typically an octet (eight electrons) in the outermost shell. If the outermost shell is nearly full, the atom gains the necessary number of electrons to complete its octet, and this number defines its valency.
Think of an octet like a dining table with 8 seats; if 7 seats are taken, you only need 1 more person to complete the group. The number of people needed to fill the empty seats represents the element's 'combining capacity' or valency.
Octet Rule: 'Eight is Great'—atoms strive for 8 to be stable.
V=8−Nv — where V is valency and Nv is the number of valence electrons (for Nv>4)
V=Nv — where V is valency and Nv is the number of valence electrons (for Nv≤4)
According to the Octet Rule, atoms are most stable when they have a full outer shell (usually 8 electrons). Elements with 5, 6, or 7 valence electrons tend to gain electrons to reach the stable configuration of a noble gas. The number of electrons gained is equal to 8−(valence electrons), which dictates the valency of the element.
Valency is a measure of an atom's ability to combine with other atoms.
Noble gases have a valency of 0 because their octet is already complete.
The octet rule is fundamental for explaining chemical bonding in main-group elements.
Predicts chemical reactivity
Explains the formation of chemical compounds
Does not account for transition metals with variable valencies
Fails for hypervalent molecules (e.g., SF6)
Predicting the formulas of ionic compounds
Understanding the reactivity of non-metals like Halogens
Elements like Chlorine (Group 17) have 7 valence electrons, so they gain 1 electron to achieve stability, resulting in a valency of 1.
Option A, B, and C relate to the nucleus or total mass, which determine the identity and isotope of an element, not its chemical bonding behavior.
D is correct — The valency of an element with a nearly full outermost shell is determined by the number of electrons it must gain to complete its octet of 8 electrons.
Always remember that for non-metals (Group 15-17), valency is often calculated as 8 minus the group number, whereas for metals, it is simply the group number (up to Group 13).