Answer:
They have completely filled outermost shell
Explanation:
The noble gases are the rarest and occur in trace amounts in the atmosphere because they have completely filled outermost and this makes them unreactive with other elements.
Elements become abundant as they combine with other species to form compounds.
Noble gases on the other hand have a high level of stability and do not readily combine with other species.
Some of these gases are :
Helium
Neon
Argon
Krypton
Xenon
Radon
They have very high ionization energy and very low electron affinity and so will not readily react.
Answer:
B
Explanation:
The wolf with shorter legs would not be an adaptation but more of a birth defect as a wolf with short legs would be at a disadvantage.
Answer:
c
Explanation:
the positive charges of the nuclear and the negative charges of delocalized electrons
Answer:
d
Explanation:
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Answer:
CCl4- tetrahedral bond angle 109°
PF3 - trigonal pyramidal bond angles less than 109°
OF2- Bent with bond angle much less than 109°
I3 - linear with bond angles = 180°
A molecule with two double bonds and no lone pairs - linear molecule with bond angle =180°
Explanation:
Valence shell electron-pair repulsion theory (VSEPR theory) helps us to predict the molecular shape, including bond angles around a central atom, of a molecule by examination of the number of bonds and lone electron pairs in its Lewis structure. The VSEPR model assumes that electron pairs in the valence shell of a central atom will adopt an arrangement which tends to minimize repulsions between these electron pairs by maximizing the distance between them. The electrons in the valence shell of a central atom are either bonding pairs of electrons, located primarily between bonded atoms, or lone pairs. The electrostatic repulsion of these electrons is reduced when the various regions of high electron density assume positions as far apart from each other as possible.
Lone pairs and multiple bonds are known to cause more repulsion than single bonds and bond pairs. Hence the presence of lone pairs or multiple bonds tend to distort the molecular geometry geometry away from that predicted on the basis of VSEPR theory. For instance CCl4 is tetrahedral with no lone pair and four regions of electron density around the central atom. This is the expected geometry. However OF2 also has four regions of electron density but has a bent structure. The molecule has four regions of electron density but two of them are lone pairs causing more repulsion. Hence the observed bond angle is less than 109°.
