The symptoms of influenza (flu) appear suddenly and often include: 1  Fever of 100.4Â°F (38Â°C) to 104Â°F (40Â°C), which can reach 106Â°F (41Â°C) when symptoms first develop. 2  Body aches and muscle pain (often severe), commonly in the back, arms, or legs. 3  Headache. Pain when you move your eyes.
A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electrostatic force of attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction. double bond between two atoms is formed by the sharing of two pairs of electrons, one in a sigma bond and one in a pi bond, with electron density concentrated on two opposite sides of the internuclear axis.
Hydrogen bond: A chemical bond formed between two atoms or ions with opposite charges. Ionic bond: A chemical bond formed when one atom gains and a second atom loses electrons. An ion is a molecule or atom that has lost one or more electrons and is, therefore, electrically charged.