Why is oxygen classed as an element but carbon dioxide is crassed as a compound ?

The is a particle with one unit of positive charge a. proton b. positron c. electron d. nucleus awnser quick it is a important science test!

Gwhich r group would most likely be found in a hydrophobic area of the tertiary structure of a globular protein? which r group would most likely be found in a hydrophobic area of the tertiary structure of a globular protein? −ch2−oh −ch2−o||c−nh2 −ch2−coo− −ch2−ch2−ch2−ch2−n+h3

Chromosome 17 is made of over million base pairs.