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Biology
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CHEMISTRY Essential Question: What is the difference between an atom, an element, and a compound?
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Atoms
Atoms
The study of chemistry begins with the basic unit of matter, the atom.
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Atoms
Placed side by side, 100 million atoms would make a row only about 1 centimeter long.
Atoms contain subatomic particles that are even smaller.
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Atoms
The subatomic particles that make up atoms are
protons
neutrons
electrons
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Atoms
The subatomic particles in a helium atom.
Helium atoms contain protons, neutrons, and electrons. The positively charged protons and uncharged neutrons are bound together in the dense nucleus, while the negatively charged electrons move in the space around the nucleus.
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Elements and Isotopes
Elements and Isotopes
A chemical element is a pure substance that consists entirely of one type of atom.
C stands for carbon.
Na stands for sodium.
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Elements and Isotopes
The number of protons in an atom of an element is the element's atomic number.
Commonly found in living organisms:
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Chemical Compounds
Chemical Compounds
A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions.
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Chemical Compounds
Chemical Formula
Water
H2O
Table Salt
NaCl
Hydrochloric Acid
HCl
Glucose
C6H12O6
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Chemical Bonds
Chemical Bonds
The atoms in compounds are held together by chemical bonds.
The electrons that are available to form bonds are called valence electrons.
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Chemical Bonds
Ionic Bonds
An ionic bond is formed when one or more electrons are transferred from one atom to another.
These positively and negatively charged atoms are known as ions.
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Chemical Bonds
Sodium atom (Na)
Sodium ion (Cl-)
Sodium ion (Na+)
Sodium atom (Cl)
Protons
Electrons
Charge
Protons
Electrons
Charge
Protons
Electrons
Charge
Protons
Electrons
Charge
The chemical bond in which electrons are transferred from one atom to another is called an ionic bond. The compound sodium chloride forms when sodium loses its valence electron to chlorine.
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Chemical Bonds
Covalent Bonds
Sometimes electrons are shared by atoms instead of being transferred.
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Chemical Bonds
A covalent bond forms when electrons are shared between atoms.
single covalent bond
double bond
triple bond
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Chemical Bonds
The structure that results when atoms are joined together by covalent bonds is called a molecule.
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17. The Chemistry of Carbon
Organic chemistry is the study of all compounds that contain bonds between carbon atoms.
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Four groups of organic compounds found in living things are:
carbohydrates
lipids
nucleic acids
proteins
Macromolecules
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