Introduction to Chemistry Chapter 6 p. 148

Exploration Question! Why are LIVING things so different from NONLIVING things. Why are LIVING things so different from NONLIVING things. One way is to examine the chemical and molecular levels. One way is to examine the chemical and molecular levels.

Atoms and Compounds Chemical Element - a substance that cannot be broken down into any other substance. Chemical Element - a substance that cannot be broken down into any other substance. Atom-smallest unit of a chemical element Atom-smallest unit of a chemical element

Atom Every atom contains a nucleus Every atom contains a nucleus It accounts for about 99.9% of the atoms mass but only takes up a little space/volume. It accounts for about 99.9% of the atoms mass but only takes up a little space/volume. The nucleus contains two types of subatomic particles that have approximately the same mass The nucleus contains two types of subatomic particles that have approximately the same mass Proton – positive charge Proton – positive charge Neutron – no charge Neutron – no charge

Electron A third type of subatomic particle is found surrounding the nucleus in clouds of pathways called orbitals A third type of subatomic particle is found surrounding the nucleus in clouds of pathways called orbitals Electron Electron Negative Charge Negative Charge Because opposites attract, the strong charge of the nucleus helps to keep the electrons in their orbitals. Because opposites attract, the strong charge of the nucleus helps to keep the electrons in their orbitals.

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Why are atoms different? The key difference between atoms of different elements is the number of protons and electrons they contain. The key difference between atoms of different elements is the number of protons and electrons they contain.

Bonding and Compounds Chemical Bonds – the links between atoms Chemical Bonds – the links between atoms Chemical Compound – a substance formed by the bonding of atoms in definite proportions Chemical Compound – a substance formed by the bonding of atoms in definite proportions Water, salt, sugar are all chemical compounds Water, salt, sugar are all chemical compounds

Ionic bonds The strong attraction between oppositely charged ions is called an ionic bond The strong attraction between oppositely charged ions is called an ionic bond Sodium (Na+) and Chloride (Cl-) become more stable when one electron transfers from the sodium ion to the chlorine atom Sodium (Na+) and Chloride (Cl-) become more stable when one electron transfers from the sodium ion to the chlorine atom As a result, both atoms become ions As a result, both atoms become ions VIDEO VIDEO VIDEO

Covalent Bonds In a covalent bond, electrons are shared between two atoms. In a covalent bond, electrons are shared between two atoms. The more electrons in the covalent bond the stronger the bond and the more stable the arrangement The more electrons in the covalent bond the stronger the bond and the more stable the arrangement A group of atoms united by covalent bonds is called a Molecule. A group of atoms united by covalent bonds is called a Molecule. 2 electrons (single bond) 2 electrons (single bond) 4 electrons (double bond) 4 electrons (double bond) 6 electrons (triple bond) 6 electrons (triple bond) VIDEO VIDEO VIDEO

Chemical Formulas Indicates the elements that form the compound and the proportions in which they combine Indicates the elements that form the compound and the proportions in which they combine Sodium Chloride =NaCl Sodium Chloride =NaCl Chemical Formulas also indicate the numbers of each atom in the molecule Chemical Formulas also indicate the numbers of each atom in the molecule C 6 H 12 O 6 C 6 H 12 O 6 6 Carbons, 12 Hydrogens, 6 Oxygens 6 Carbons, 12 Hydrogens, 6 Oxygens

The water molecule H 2 O contains 3 atoms H 2 O contains 3 atoms We call water a polar molecule We call water a polar molecule Molecules without positive and negative ends are called nonpolar Molecules without positive and negative ends are called nonpolar

Solutions When water dissolves a substance, the liquid that results is called a solution. When water dissolves a substance, the liquid that results is called a solution.

Chemistry in Biology Homogenous Mixtures  A mixture that has a uniform composition throughout  solvent  a substance in which another substance is dissolved.  solute  the substance that is dissolved in the solvent. Food coloring dissolved in water forms a homogenous mixture. 6.3 Water and Solutions Chapter 6

Chemistry in Biology Heterogeneous Mixtures  the components remain distinct. A salad is a heterogeneous mixture. 6.3 Water and Solutions Chapter 6

Chemistry in Biology  Substances that release hydrogen ions (H + ) when dissolved in water are called acids.  HCl  H+ + Cl-  Substances that release hydroxide ions (OH – ) when dissolved in water are called bases.  NaOH  Na+ + OH- Acids and Bases 6.3 Water and Solutions Chapter 6

Chemistry in Biology  The measure of concentration of H + in a solution is called pH.  Acidic solutions have pH values lower than 7.  Basic solutions have pH values higher than 7. pH and Buffers 6.3 Water and Solutions Chapter 6

Chemistry in Biology  Buffers  acids or bases to keep the pH within a particular range.  will either raise or lower the pH 6.3 Water and Solutions Chapter 6