Meningioma; Synonyms: Meningeal tumor: A contrast-enhanced CT scan of the brain, demonstrating the appearance of a meningioma: Specialty: Neurosurgery: Symptoms: None, seizures, dementia, trouble talking, vision problems, one sided weakness: Usual onset: Adults: Types: Grade I, II, III: Risk factors: Ionizing radiation, family history: Diagnostic method
A polar covalent bond shares electrons unequally. Because of this unequal sharing, one end of the molecule is slightly positive, and the other end slightly negative. Edit
Nonpolar bonds mostly exist between atoms of the same element. For example, oxygen contains six electrons in its outer shell. To gain a full outer shell of eight electrons, oxygen atoms form double bonds with other oxygen atoms. Because they are identical atoms, they share the four electrons equally. When atoms of two different elements share electrons, they form polar covalent bonds. In polar covalent bonds, the shared electrons spend more of their time near one atom than the other, resulting in an uneven sharing and a partial charge on both atoms in the bond. Water is an example of a polar covalent bond.