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Water is a polar molecule, with the hydrogen atoms acquiring a partial positive charge and the oxygen a partial negative charge. This occurs because the nucleus of the oxygen atom is more attractive to the electrons of the hydrogen atoms than the hydrogen nucleus is to the oxygen’s electrons. Thus oxygen has a higher electronegativity    than hydrogen and the shared electrons spend more time in the vicinity of the oxygen nucleus than they do near the nucleus of the hydrogen atoms, giving the atoms of oxygen and hydrogen slightly negative and positive charges, respectively. Another way of stating this is that the probability of finding a shared electron near an oxygen nucleus is more likely than finding it near a hydrogen nucleus. Either way, the atom’s relative electronegativity contributes to the development of partial charges whenever one element is significantly more electronegative than the other, and the charges generated by these polar bonds may then be used for the formation of hydrogen bonds based on the attraction of opposite partial charges. (Hydrogen bonds, which are discussed in detail below, are weak bonds between slightly positively charged hydrogen atoms to slightly negatively charged atoms in other molecules.) Since macromolecules often have atoms within them that differ in electronegativity, polar bonds are often present in organic molecules.

Nonpolar covalent bonds

Nonpolar covalent bonds form between two atoms of the same element or between different elements that share electrons equally. For example, molecular oxygen (O 2 ) is nonpolar because the electrons will be equally distributed between the two oxygen atoms.

Another example of a nonpolar covalent bond is methane (CH 4 ), also shown in [link] . Carbon has four electrons in its outermost shell and needs four more to fill it. It gets these four from four hydrogen atoms, each atom providing one, making a stable outer shell of eight electrons. Carbon and hydrogen do not have the same electronegativity but are similar; thus, nonpolar bonds form. The hydrogen atoms each need one electron for their outermost shell, which is filled when it contains two electrons. These elements share the electrons equally among the carbons and the hydrogen atoms, creating a nonpolar covalent molecule.

Table compares water, methane and carbon dioxide molecules. In water, oxygen has a stronger pull on electrons than hydrogen resulting in a polar covalent O-H bond. Likewise in carbon dioxide the oxygen has a stronger pull on electrons than carbon and the bond is polar covalent. However, water has a bent shape because two lone pairs of electrons push the hydrogen atoms together so the molecule is polar. By contrast carbon dioxide has two double bonds that repel each other, resulting in a linear shape. The polar bonds in carbon dioxide cancel each other out, resulting in a nonpolar molecule. In methane, the bond between carbon and hydrogen is nonpolar and the molecule is a symmetrical tetrahedron with hydrogens spaced as far apart as possible on the three-dimensional sphere. Since methane is symmetrical with nonpolar bonds, it is a nonpolar molecule.
Whether a molecule is polar or nonpolar depends both on bond type and molecular shape. Both water and carbon dioxide have polar covalent bonds, but carbon dioxide is linear, so the partial charges on the molecule cancel each other out.

Hydrogen bonds and van der waals interactions

Ionic and covalent bonds between elements require energy to break. Ionic bonds are not as strong as covalent, which determines their behavior in biological systems. However, not all bonds are ionic or covalent bonds. Weaker bonds can also form between molecules. Two weak bonds that occur frequently are hydrogen bonds and van der Waals interactions. Without these two types of bonds, life as we know it would not exist. Hydrogen bonds provide many of the critical, life-sustaining properties of water and also stabilize the structures of proteins and DNA, the building block of cells.

Questions & Answers

what do you guys understand about evolution?
Kiana Reply
it's a process or analayzing some program
Fahamia
but am not sure if some know plz let share
Fahamia
is a study of
Sarah
unfolding or unrolling hence the process of development of growth
Sarah
why are diagrams not available
Evans Reply
How can nucleotide molecules of DNA be constructed?construct a six molecules of DNA?
Julia Reply
describe the breathing mechanism in the body fish.
Jackson Reply
what is genetics.
Jackson
the study of hereditary
Julia
state the importance of biodiversity of organisms in an area?
Chris Reply
what is biology
Adam Reply
Biology is the study of living things.
Patrick
what are some of the branches of biology?
Jackson
anatomy,genetics,parasitology
Evans
what is meosis
Mabatho Reply
did you mean meiosis? meiosis this is the type of cell division where one diploid parent cell produces two daughter cells that are haploid and genetically different from the parent cell.
Patrick
thankyou
Mabatho
I'm struggling to understand genetics
Mabatho
Am also struggling as well
Patrick
nothing comes on a silver platter, you need to put effort in everything you are doing not forgetting God. study as if there is no tomorrow. "Suffer now and enjoy the future"
Patrick
true bro
Patrick
exactly brother
Odhiambo
Glory to God
Patrick
Thanks Pat🙏
Mabatho
you're welcome
Patrick
what's a nervous system
tessy Reply
what's the human brain
tessy
the structure of paramecium
Charity Reply
yes
Sarah
Ho
Nevers
what is endocytosis
Stephen Reply
what is the meaning of adrenocorticotropic
Abigail Reply
adrenocorticotropic is stimulating or acting on the adrenal cortex.
Belinda
ok thanks
Abigail
What is science of biology
Thando Reply
The study 📓 of leaving things
John
how does a parasite benefit from its mode of living?
Abuk Reply
why are the images n diagrams unable to be seen?
Abuk
where are the illustrations
Simon
a parasite gets protection, food, shelter
Anguson
human being
Jackson
what is Alimentary canal?
Princess Reply
what is commenialism
jamex Reply
Do you mean commensalism?,it is a feeding relationship that has to do with two different species feeding, that is one is benefiting and the other is unaffected.
hamidat
commensalism is a feeding relationship that has to do with different species feeding, one is gaining and the other is unaffected.
hamidat

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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