The structure of matter

1
Chapter 4

• The structure of matter

2
4.1 Compounds MoleculesOBJECTIVES

• Distinguish between compounds mixtures
• Relate the chemical formula of a compound to the
  relative numbers of atoms or ions present in the
  compound
• Use models to visualize a compounds chemical
  structure
• Describe how the chemical structure of a compound
  affects its properties.

3
Key Terms

• Chemical bond
• Chemical structure
• Bond length
• Bond angle

4
What are compounds?

• 2 elements combined
• Is the compound identical to the element?
• ___________
• Compounds are always made of the same elements in
  the same _________
• Ex. Water is always made of 2 ________ atoms and
  1 ________ atom

5
What is a chemical bond?

• Chemical bonds separate compounds from
  ___________
• The forces that hold bonds together
• Does a compound ALWAYS have the same chemical
  formula? __________
• Chemical structure shows the _________ within a
  compound (how atoms or ions are connected)

6
What does the chemical formula show?

• Ex H20/NaCl
• A chemical formula shows the _____ __________
  of atoms _______ making up the simplest unit of
  the compound

7
Did you know?

• Atoms in a compound and the way they are arranged
  determine a compounds property?
• 2 terms tell the positions of atoms to one
  another in a compound? What are they?
• BOND LENGTH- (tells how strong a bond is) -
• BOND ANGLES-

8
How does structure affect properties?

• Some are networks of bonded atoms
• Some are networks of and ions (high melting
  and boiling points)
• Networks are STRONG solids
• Ex Quartz SiO2 Sand SiO2
• Some are many separate molecules these are
  weaker
• Ex Sugar C, H, O

9
Molecules are affected by

• Intermolecular forces (positive/negative parts)
• Inter between
• Ex. Interstate -
• Intramolecular forces (covalent bonds)
• Intra within
• Ex. Intrastate -

10
4.2 Ionic Covalent BondingObjectives

• Explain why atoms sometimes join to form bonds
• Explain why some atoms transfer their valence
  electrons to form ionic bonds, while other atoms
  share valence electrons to form covalent bonds
• Differentiate between ionic,covalent, and
  metallic bonds
• Compare the properties of substances with
  different types of bonds

11
Key Terms

• Ionic Bond
• Metallic Bond
• Covalent Bond
• Polyatomic Ions

12
What holds bonded atoms together?

• The outermost energy level is full (share)
• Atoms bond when valence e-s interact
• They are less reactive when full
• Positive and negative atoms are attracted to each
  other (think of magnets) THEY SHARE E-s
• 2. Bonds can bend and stretch without breaking

13
Ionic Bonds

• REMEMBER CATIONS/ANIONS
• Formed between oppositely charged ions
• Metal elements form positively charged ions
• Ex. Sodium (Na) and Calcium (Ca)
• Nonmetal elements form negatively charged ions
• Chlorine (Cl) and Oxygen (O)

14

• Ionic bonds are formed by the transfer of
  electrons
• Dont share e-s they TRANSFER
• Both ions have filled outermost energy levels
• Result 1 pos. ion 1 neg. ion
• They attract each other --- form a bond

15

• Ionic compounds are the form of NETWORKS not
  molecules
• When melted or dissolved in water, ionic
  compounds conduct electricity
• Solid what do the molecules look like?
• Liquid what do they look like
• Why able to conduct electricity?

16
Metallic Bonds

• Conduct electricity when SOLID
• Flexible bend and stretch without breaking
• Examples
• Electrons move freely between metal atoms
• They are attracted to each other and so the
  outermost energy levels overlap
• Electrons are free to move back and forth good
  conductor and flexibility

17
Covalent Bonds

• Made of molecules (Ex water and sugar)
• Non metal atoms
• Compounds that are networks of BONDED atoms are
  held together by covalent bonds (silicon dioxide
  SiO2)
• Compounds can be solid, liquid or gas
• (Exception cmpds w/ network structures)

18
Covalent Bonds contd

• Low melting points
• Cmpds made of molecules are free to move when
• Dissolved in water
• Melted
• Remain intact
• DO NOT conduct electricity not charged

19
Covalent bonds contd

• Atoms joined by covalent bonds share pairs of
  valence electrons
• Ex Cl atom Cl atom
• Nonpolar covalent bond
• Cl-Cl
• Single line indicates 2 shared e-s

20
Covalent Bonds contd

• Atoms may share more than 1 pair of e-s
• ClCl is a double covalent bond (4 e- 2 pr)
• ClCl is a triple covalent bond (6 e- 3 pr)
• These are shorter than single bonds
• Triple is stronger than double
• Atoms dont always share e-s equally
• 2 different atoms sharing Polar covalent bond

21
Polyatomic Ions

• Compounds that have BOTH ionic covalent bonds
• They have lost or gained electrons

22
Polyatomic Ions Contd

• There are many polyatomic ions
• Opp. Charged P. ions can bond to form cmpds.
• Parentheses group the atoms of a polyatomic ion
• ( ) tells you this acts like a single ion
• If there is a 11 ratio then no ( )
• Charge applies to the entire ion.

23
Polyatomic Ions contd

• Some polyatomic anion names relate to their
  oxygen content
• -ite or ate
• -ate ion with 1 more Oxygen atom
• -ite ion with 1 less Oxygen atom
• Not all P.A. ions follow the naming rules
• Ex hydroxide (OH-) or cyanide (CN-)

24
4.3 Compound Names Formulas Objectives

• Name single ionic and covalent compounds
• Predict the charge of a transition metal cation
  in an ionic compound
• Write chemical formulas for simple ionic
  compounds
• Distinguish a covalent compounds empirical
  formula from its molecular formula

25
Key Terms

• Empirical Formula
• Molecular Formula

26
Naming Ionic Compounds

• Formed by the strong attractions between cations
  and anions
• Both ions are impt. to the structure so they are
  incl. in the name

27
Naming contd

• Names of ionic compounds include the ions that
  make them up
• Anion made of 1 element has a name similar to it,
  but the ending is different
• Ends in ide
• Ex. Flourine becomes Flouride
• Cation same as the name of the element
• Group 1 1, Group 2 2

28
Naming contd

• Some cation names must show their charge
• FeO Fe2O3 is iron oxide
• This is a transition metal and can form several
  cations (each with a different charge) so it has
  to be identified another way
• Fe2O3 has Fe 3 ions so it is iron(III) oxide
• FeO has Fe 2 ions so it is iron(II) oxide

29
Naming contd

• Determining the charge of a transition metal
  cation
• Ionic compounds (like other cmpds) have a total
  charge of 0
• The total charges must the total charges
• Writing Formulas for ionic cmpds

30

• Naming covalent cmpds
• Different rules than ionic cmpds
• Numerical prefixes are used to name covalent
  cmpds of 2 elements
• Whats a prefix?
• The prefix tells how many atoms of each element
  are in the molecule
• If there is only 1 atom of the 1st element it
  doesnt get a prefix
• The element farther to the right in the periodic
  table is named 2nd and ends in -ide

31
Chemical Formulas for Covalent Compounds

• A compounds simplest formula is its empirical
  formula
• The smallest whole-number ratio of atoms in a
  compound (21)
• Most ionic cmpds are empirical formulas
• Different compounds can have the same empirical
  formula
• These only represent a ratio of atoms

32

• Molecular formulas are determined from empirical
  formulas
• Formaldehyde, acetic acid, glucose are all
  covalent compounds made of MOLECULES
• They all have the same EMPIRICAL formula, but
  their own MOLECULAR formula
• Molecular formula tells how many molecules are in
  1 molecule of the compound

33
Organic Compounds

• Organic describes certain cmpds
• A covalently bonded cmpd made of molecules
• Contain C and, almost always, H
• Sometimes contain O,N,S,Ph

34

• Alkanes have single covalent bonds
• Hydrocarbons C-C or C-H
• Arrangements of carbon atoms in alkanes
• Methane, Ethane, Propane C atoms line up in a
  row
• 3 bonded C atoms dont always line up in a row
• If line up N-alkane/normal alkane

35

• Carbon atoms form 4 covalent bonds in organic
  cmpds
• Hydrocarbon Cs Hs
• Methane CH4 is the simplest
• C atom can NEVER form more than 4 bonds

36

• Alkane chemical formulas
• End in -ane
• H atoms is always 2 more than twice the of C
  atoms (CnH(2n2))
• Alkene(CnH2n) Alkyne (CnH2n-2))
• Alkenes have double C-C bonds
• Hydrocarbons
• At least 1 double covalent bond btwn C atoms
• CC
• End in -ene