3minute warmup: atomic definitions section 1

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3-minute warm-up atomic definitions (section 1)

• Match each definition to a term.
• Definitions
• 1. a negatively charged particle that moves
  around an atoms nucleus
• 2. an atom that has lost an electron
• 3. an atom that has gained an electron
• Terms
• a. electron
• b. negative ion
• c. positive ion

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Unit 2 Chemical InteractionsChapter 2 Chemical
Bonds and Compounds

• Section 2 Chemical bonds hold
• compounds together.

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Then and Now

• BEFORE, you learned
• Elements combine to form compounds
• Electrons are located in a cloud around the
  nucleus
• Atoms can lose or gain electrons to form ions

• NOW, you will learn
• How electrons are involved in chemical bonding
• About the different types
• of chemical bonds
• How chemical bonds affect structure

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Set Learning Goals

• Students will
• Explain how electrons are involved in chemical
  bonding.
• Describe what the different types of chemical
  bonds are.
• Determine how chemical bonds affect structure.
• Observe how a crystal grows in an experiment.

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Section 2.2 Vocabulary

• ionic bond
• covalent bond
• molecule
• polar covalent bond

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Chemical Bonds

• What do you think is going to cause elements to
  bond and interact with each other protons,
  neutrons, or electrons? Why?
• Electrons
• __________________________________________________
  __________________________

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Bonds Atoms transferelectrons

• Ions
• Positive ions
• Lose electrons
• Negative ions
• Gain electrons
• Ions dont form by themselves they form in
  pairs (giving an electron to another element)
• Metals (Groups 1 and 2) will lose 1 or 2
  electrons
• Nonmetals (Groups 16 and 17) will gain 1 or 2
  electrons

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Ionic Bonds what happens

• Sodium gives an electron to chlorine
• Sodium gets smaller, chlorine gets larger
• Sodium becomes a positive ion, chlorine becomes a
  negative ion
• Opposites attract
• This attraction is ionic bonding

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Attraction EVERYwhere

• Electrical forces go in all directions
• Each positive ion is surrounded by six negative
  ions
• This is what gives salt its cubic shape
• Ionic bonds are very stable

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Naming Ionic Compounds

• Positive ion
• Use the full name
• Negative ion
• Drop the end and add ide to it
• Example NaCl
• Positive ion sodium
• Negative ion chlorine drop end and get
  chloride
• Compound is called potassium chloride

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Sharing Electrons Covalent bonding

• Usually happens with nonmetals
• Sharing electrons between two atoms is a covalent
  bond
• Two models
• Overlapping electron clouds
• Ball and stick model

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Number of bonds

• Atoms can only share as many electrons as are
  available
• Group 18 shares none, cant bond
• Group 17 shares 1, one bond
• Group 16 shares 2, two bonds
• Group 15 shares 3, three bonds
• Group 14 shares 4, four bonds

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Methane

• Carbon group 14, shares 4 electrons, has 4 bonds

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More than their share

• Atoms can share more than one pair of electrons
• Double bonds (two pairs of electrons)
• Triple bonds (three pairs of electrons)
• Examples

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Whats a molecule?

• A group of atoms held together by covalent bonds
• Most molecules contain more than one element
• water (H2O), ammonia (NH3), and methane (CH4)
• Some are single elements
• H2, N2, O2, F2, Cl2, Br2, and I2

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What is the name ofMgO?

• magnesium oxide

What type of bond holds a crystal together?

• ionic

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What type of bond is formed when electrons are
shared?

• covalent

What is a molecule?

• a group of atoms held together by covalent bonds

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Weird Covalent Bonds

• Sometimes atoms attract more to a specific
  nucleus (back to the opposites attract thing).
• Electrons are shared unevenly
• Polar covalent bond
• Water has a positive and negative side as a
  result

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Structure Ionic Compounds

• Usually have a crystal shape
• Usually rigid
• Means they break when enough pressure is applied

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Structure Covalent Compounds

• Can exist individually
• Shape depends on the atom and the bonds holding
  it
• Linear, bent, pyramidal, tetrahedral (big one)

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Molecular Structure

• Effects properties
• Smell (specific shapes smell specific ways)
• Drugs (specific shapes fit different receptors in
  our bodies)

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Questions 2.2.2

• KEY CONCEPTS
• 1. What part of an atom is involved in chemical
  bonding?
• 2. How are ionic bonds and covalent bonds
  different?
• 3. Describe two ways that crystal and molecular
  structures affect the properties of ionic and
  covalent compounds.
• .

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• CRITICAL THINKING
• 4. Analyze Would you expect the bonds in ammonia
  to be polar covalent? Why or why not?
• 5. Infer What kind of bond would you expect atoms
  of strontium and iodine to form? Why? Write the
  formula and name the compound.
• CHALLENGE
• 6. Conclude Is the element silicon likely to form
  ionic or covalent bonds? Explain.
• .