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CHAPTER 2-1

CHAPTER 2-1. FEDEROFF. ATOMS. Atom – is the basic unit of matter Ex. Democritus – breaking a piece of chalk, when is it not chalk anymore? Until atomos “unable to be cut” An atom is very small. 100 million atoms make up about 1 cm. ATOMS.

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CHAPTER 2-1

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  1. CHAPTER 2-1 FEDEROFF

  2. ATOMS • Atom – is the basic unit of matter • Ex. Democritus – breaking a piece of chalk, when is it not chalk anymore? Until atomos “unable to be cut” • An atom is very small. 100 million atoms make up about 1 cm.

  3. ATOMS • Atoms are made of smaller subatomic particles: protons, neutrons and electrons. • Protons have a positive charge, neutrons a neutral charge and together they make up the nucleus of an atom • Electrons are negatively charged and much smaller than protons • Atoms have a neutral charge, equal number of electrons and protons

  4. ELEMENT • An element is a pure substance made up of just one type of atom • Elements have a one or two letter symbol • The number of protons equals the atomic number of the element

  5. ELEMENT • Atoms of the same element that differ in the number of neutrons they contain are known as isotopes. • Isotopes are identified by their mass number • Isotopes of an element are similar because they have the same number of electrons; all isotopes of an element have the same chemical properties. • Radioactive isotopes are important to use for dating and labels to follow the movement of substances within organisms.

  6. CHEMICAL COMPOUNDS • A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions. • Written in shorthand known as a chemical formula

  7. CHEMICAL COMPOUNDS • The physical and chemical properties of a compound are usually very different from those of the elements from which it is formed. • Ex. Sodium Chloride – Sodium and Chlorine

  8. CHEMICAL BONDS • The main types of chemical bonds are ionic bonds and covalent bonds. • An ionic bond is formed when one or more electrons are transferred from one atom to another. • Positively and negatively charge atoms are known as ions.

  9. CHEMICAL BONDS • A covalent bond is formed when one or more pairs of electrons are shared between two atoms. • Can be a single, double or triple bond

  10. CHEMICAL BONDS • A molecule is the smallest unit of most compounds. • Ex. Water – H2O • Doesn’t usually share electrons equally between the two atoms

  11. CHEMICAL COMPOUNDS • Van der Waals forces are a type of intermolecular interaction in which molecules that are close together, have a slight attraction that develops between the oppositely charge regions of nearby molecules. • Ex. Tokay gecko

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