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Honors Biology Chapter 2. The Chemistry Of life. The Nature of Matter. Essential Question: How would you explain the relationship between atoms, elements, and compounds?. Atoms. smallest unit of matter each element has its own unique # of protons (atomic #). Elements.
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Honors BiologyChapter 2 The Chemistry Of life
The Nature of Matter • Essential Question: • How would you explain the relationship between atoms, elements, and compounds?
Atoms smallest unit of matter each element has its own unique # of protons (atomic #)
Elements • Only ~ 24 elements found in living things • 4 most abundant: • Oxygen • Carbon • Hydrogen • Nitrogen
Isotopes atoms of same element with different # of neutrons #p + #n = atomic mass (mass #)
Radioactive Isotopes some isotopes have unstable nuclei so they undergo “decay”
Chemical Cpds compound: substance formed by chemical combination of 2 or more elements in definite proportions cpd has different properties than elements alone had
Chemical Bonds Atoms form chemical bonds with other atoms to ________________. The 2 main types of bonds are ________ and ____________.
Chemical Bonds Covalent Bonds Polar Covalent Bonds share valence e- unequal sharing e-
Ionic bonds • transfer of e- atom with a charge (ion) • (+) ions = cations • (-) ions = anions • opposite charges attract • charges must be balanced • stronger bonds than covalent
van der Waals Forces • Because atoms do not share e- equally, there are polar bonds • This causes the (+) end of one molecule to be attracted to the (-) end of another molecule • This attraction is called van derwaals forces • Very weak compared to covalent bonds but are still able to hold molecules together