Chapter 2: The Chemistry Of Life. Atoms: What is an atom? –The basic unit of matter Incredibly...
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Transcript of Chapter 2: The Chemistry Of Life. Atoms: What is an atom? –The basic unit of matter Incredibly...
![Page 1: Chapter 2: The Chemistry Of Life. Atoms: What is an atom? –The basic unit of matter Incredibly small: 100,000,000 atoms lined up in a row would only be.](https://reader031.fdocuments.in/reader031/viewer/2022013122/56649e155503460f94b002fe/html5/thumbnails/1.jpg)
Chapter 2: The Chapter 2: The Chemistry Of LifeChemistry Of LifeChapter 2: The Chapter 2: The
Chemistry Of LifeChemistry Of Life
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Atoms:• What is an atom?
– The basic unit of matter• Incredibly small: 100,000,000
atoms lined up in a row would only be the width of your pinky finger!
• But there are even smaller particles that make up atoms.
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Subatomic Particles• Three types: Protons, Neutrons,
Electrons• Protons:
– Positively charged• Neutrons:
– Neutral in charge• Electrons:
– Negatively charged particles– are about .00054th the size of a proton or
neutron.
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Subatomic particles Cont’d.
• Protons and neutrons have about the same mass.
• Nucleus: located at the center of the atom and is made up of protons and neutrons.
• Electrons are in constant motion and surround the nucleus like a cloud– They are attracted to the positive
nucleus but are not part of the nucleus because they are in constant motion
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• Atoms have equal numbers of protons and electrons so they are neutral in charge.
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What is a Chemical Element?
• A chemical element is a pure substance that is made entirely out of one type of atom.
• Elements are represented by a one or two letter symbol. – Ex: C is the symbol for carbon.– Pb is the symbol for lead.
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Elements and Isotopes• The number of protons in an element is that
element’s atomic number. • Atoms of an element can have different
numbers of neutrons.• Example: some atoms of carbon have 6
neutrons and some have seven– These are called isotopes
• Isotopes occur when atoms of the same element have a different number of neutrons
• Radioactive isotopes: meaning their nuclei are unstable and break down at a constant rate over time.
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Let’s look at some examples of Isotopes
• Red = protons
• Green = neutrons
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• In nature, most elements are found combined with other elements in a compound.
• What is a compound?• A compound is a substance that
is formed by the chemical combination of 2 or more elements in definite proportions. – Ex: H20 contains 2 atoms of Hydrogen
and one atom of Oxygen.
Chemical Compounds
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Chemical Bonds• Atoms in compounds
are held together by chemical bonds.
Chemical bond
Atom 2
Atom 1
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Ionic Bonding• Ionic bonds are formed when one
or more electrons are transferred from one atom to the other
• Let’s look at an example:
• Positively and negatively charged atoms are known as ions.
•Na+ + Cl- NaCl
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Ionic Bonds Cont’d• Remember that atoms are electrically
neutral because they have equal numbers of protons and electrons
• An atom that loses electrons has a positive (+) charge, and an atom that gains electrons has a negative (-) charge
• Ionic Bonding video
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Covalent Bonding• Sometimes electrons are shared by
atoms instead of being transferred• Covalent bonding occurs when
electrons are shared between atoms• When the atoms share two electrons it
is called a single covalent bond:
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Covalent Bonding Cont’d
• When they share 4 electrons it is called a double covalent bond:
• And if they share 6 electrons it is called a triple covalent bond:
• Covalent bonding video
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• The structure that results when atoms are joined together by a covalent bond is called a molecule.
What does it all mean?
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Section 2-2: Properties of the Water Molecule
• Water molecules, like all molecules, are neutral.
• The water molecule is known as a polar molecule
• What does this mean?• It is polar because there is an uneven
distribution of electrons between the oxygen and hydrogen atoms.
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Water• Water molecules are held together
by Hydrogen Bonds which are the weakest type of bonds
• This ability to form multiple hydrogen bonds is responsible for many of water’s properties.
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Cohesion• Cohesion is an attraction between
molecules of the same substance. • Cohesion causes the molecules on the
surface of water to be drawn inward, which is why drops of water form beads on a smooth surface and why some insects can float on top of water.
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Other properties of water
• Adhesion is an attraction between molecules of different substances.
• Adhesion between water and glass causes water to rise in a narrow tube against the force of gravity. – This effect is called capillary
action.
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Solutions and Suspensions
• Water is not always pure. It is often found as part of a mixture.
• What is a mixture?– A Mixture is a material composed of
two or more elements or compounds that are physically mixed together but not chemically combined.• Ex: salt and pepper
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Two types of water mixtures
• Solutions: mixtures of two or more substances in which the molecules of the substances are evenly distributed– Ex: salt mixed into warm water
• What are some other examples of solutions?
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Solutions Cont’d.• The salt is he solute, or the
substance that is dissolved• The water is the solvent, or the
substance that dissolves the solute.
• What are the solutes/solvents in your examples?
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Suspensions• Suspensions are mixtures of
water and non-dissolved materials– Ex: blood in your body