Name 5 things that use chemistry. Copyright Pearson Prentice Hall

2-1 The Nature of Matter

Atoms: the basic unit of chemistry. Copyright Pearson Prentice Hall

Placed side by side, 100 million atoms would make a row only about 1 centimeter long. Atoms contain subatomic particles that are even smaller. Copyright Pearson Prentice Hall

The subatomic particles that make up atoms are  protons  neutrons  electrons Copyright Pearson Prentice Hall

The subatomic particles in a helium atom. Copyright Pearson Prentice Hall

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. Copyright Pearson Prentice Hall

The number of protons in an atom of an element is the element's atomic number. Commonly found in living organisms: Copyright Pearson Prentice Hall

Isotopes: Atoms of the same element that differ in the number of neutrons they contain. They have the same chemical properties. Copyright Pearson Prentice Hall

6 electrons 6 protons 8 neutrons

Radioactive Isotopes Some isotopes are radioactive, meaning that their nuclei are unstable and break down at a constant rate over time Copyright Pearson Prentice Hall

Radioactive isotopes can be used:  to determine the ages of rocks and fossils.  to treat cancer.  to kill bacteria that cause food to spoil.  as labels or “tracers” to follow the movement of substances within an organism. Copyright Pearson Prentice Hall

Chemical Compounds A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions. Copyright Pearson Prentice Hall

Chemical Formula Water H 2 O Table Salt NaCl Hydrochloric AcidHCl GlucoseC 6 H 12 O 6 Copyright Pearson Prentice Hall

Chemical Bonds The atoms in compounds are held together by chemical bonds. The electrons that are available to form bonds are called valence electrons. Copyright Pearson Prentice Hall

The main types of chemical bonds are:  ionic bonds  covalent bonds Copyright Pearson Prentice Hall

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. Copyright Pearson Prentice Hall

Protons +17 Electrons - 18 Charge -1 Protons +11 Electrons - 11 Charge 0 Protons +11 Electrons - 10 Charge +1 Protons +17 Electrons - 17 Charge 0 Sodium ion (Cl - ) Sodium atom (Na) Sodium atom (Cl) Sodium ion (Na+)

Covalent Bonds Sometimes electrons are shared by atoms instead of being transferred. Copyright Pearson Prentice Hall

A covalent bond forms when electrons are shared between atoms.  single covalent bond  double bond  triple bond Copyright Pearson Prentice Hall

The structure that results when atoms are joined together by covalent bonds is called a molecule. Copyright Pearson Prentice Hall

Van der Waals Forces When molecules are close together, a slight attraction can develop between the oppositely charged regions of nearby molecules. Copyright Pearson Prentice Hall

2-1 The particles that move around the nucleus of an atom are called  neutrons.  protons.  electrons.  isotopes. Copyright Pearson Prentice Hall

2-1 The atomic number of a carbon atom is 6. How many neutrons does the isotope carbon-14 have?  6  8  12  14 Copyright Pearson Prentice Hall

2-1 Which of the following statements about the three isotopes of carbon is true?  They are all radioactive.  They have different numbers of electrons.  They have the same chemical properties but differ in atomic mass.  They have the same number of protons and neutrons. Copyright Pearson Prentice Hall

2-1 A chemical compound consists of  Electrons mixed with neutrons.  two or more elements combined in a definite proportion.  two or more protons combined in any proportion.  at least three elements combined by ionic or covalent bonds. Copyright Pearson Prentice Hall

2-1 Van der Waals forces are the result of  unequal sharing of electrons.  ionic bonds.  the bonding of different isotopes.  the chemical combination of sodium and chlorine. Copyright Pearson Prentice Hall

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