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Physical Science The Structure of Matter. What are compounds?. When two or more elements are chemically combined Ex)NaCl (sodium chloride) salt. Chemical bonds. Chemical bond- the attractive force that holds atoms or ions together Chemical bonds distinguish mixtures from compounds

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Physical science the structure of matter

Physical ScienceThe Structure of Matter


What are compounds
What are compounds?

  • When two or more elements are chemically combined

  • Ex)NaCl (sodium chloride) salt


Chemical bonds
Chemical bonds

  • Chemical bond- the attractive force that holds atoms or ions together

  • Chemical bonds distinguish mixtures from compounds

  • Mixtures can be separated by physical means because they lack chemical bonds!


Compounds always have the same chemical formula
Compounds always have the same chemical formula

  • A chemical formula shows the types and numbers of atoms or ions making up the simplest unit of the compound.

  • Compounds are always made of the same elements in the same proportion.

  • Ex) H2O



Models of compounds
Models of Compounds

  • Ball and stick

  • Structural formulas

  • Space-filling models


How does structure affect property
How does structure affect property?

  • Compounds with network structures are strong solids with rigid structures

  • Quartz SiO2

  • Very high melting and boiling points due to strong bonds.


Compounds made up of networks bonded ions
Compounds made up of networks bonded ions

Table salt and sodium chloride in the form of regularly shaped crystals. Sodium chloride of crystals are cubed shaped.

Strong attractions between the oppositely charged ions caused the table salt and the other similar compounds to have high melting points and boiling points


Each grain of table salt is composed of a tightly packed network of Na+ ions and CI- ions

What is an Ion?


Compounds made of molecules
Compounds made of molecules network of Na+ ions and CI- ions

  • Ex) sugar is made up of molecules

  • C H O joined by bonds

  • Molecules of sugar form crystals when bonded

  • Weaker bonds

  • Lower melting and boiling points then network ion compounds


Hydrogen bonds
Hydrogen bonds network of Na+ ions and CI- ions

  • Attractions between water molecules

  • Hydrogen bonds are relatively weak

  • Low melting and boiling points


What holds bonded atoms together
What holds bonded atoms together? network of Na+ ions and CI- ions

  • Recall Three types of bonds discussed

    Ionic, Covalent, Hydrogen

  • Bonded atoms have stable electron configurations

  • Valence electrons determine reactivity!

  • They want to fill their outermost energy level, to be happy 

  • H2


Ionic bonds
Ionic Bonds network of Na+ ions and CI- ions

  • Formed between oppositely charged ions.

  • Cations-positively charged (metals)

  • Anions-negatively charged (nonmetals)

    Ionic bonds form by the transfer of electrons

    Table salt= Sodium Chloride= Na+ and Cl-

    together they form NaCl a neutral compound (no charge)



Metallic bonds
Metallic Bonds network of Na+ ions and CI- ions

  • Metals conduct electricity when they are solid, Ex) Copper Cu

  • They are malleable, can be flattened into thin sheets

  • They are ductile, can be drawn into fine wire




Covalent bonds
Covalent Bonds in the solid form

  • Covalent bond- a bond formed when atoms share one or more pairs of electrons

  • Compounds made of molecules (water and sugar) have covalent bonds

  • Most have low melting points

  • Cl2




Interpreting molecular models
Interpreting Molecular Models Ex) Cl2

  • Can have single

  • Double

  • Or

  • Triple bonds

  • Each line ( bond) represents the sharing of two electrons

  • Dots represent electrons that are not involved in bonding



Electronegativity
Electronegativity Ex) Cl2

  • Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons


  • If the atoms are equally electronegative, both have the same tendency to attract the bonding pair of electrons, and so it will be found on average half way between the two atoms. To get a bond like this, A and B would usually have to be the same atom. You will find this sort of bond in, for example, H2 or Cl2 molecules.


  • Summary tendency to attract the bonding pair of electrons, and so it will be found

  • No electronegativity difference between two atoms leads to a pure non-polar covalent bond.

  • A small electronegativity difference leads to a polar covalent bond.

  • A large electronegativity difference leads to an ionic bond.


Polyatomic ions
Polyatomic Ions tendency to attract the bonding pair of electrons, and so it will be found

  • An ion made of two or more atoms

  • Polyatomic ions have both ionic and covalent bonds

  • Parenthesis group the atoms of polyatomic ions

  • Subscripts outside the ( ) show that the number applies to the entire ion


Writing polyatomic ions
Writing Polyatomic Ions tendency to attract the bonding pair of electrons, and so it will be found

  • Charges +2, -1, +1, -2 etc…

    • Are written as super scripts Ca+

    • Subscripts show how many ions are present

    • If outside the ( ) Ex) (NH4)2 SO4

    • Instead of N2 H8 SO4

    • There are two ammonium ions per each sulfate ion

  • Subcripts show how many atoms of each element are present if there are no ( )s

    • Ex) N =1atom H4= 4 atoms CO3= 1 C & 3 O


Polyatomic ion names
Polyatomic Ion Names tendency to attract the bonding pair of electrons, and so it will be found

  • Some polyatomic anion names relate to their oxygen content

  • Most names end with –ite or –ate

  • Ion charge is the same, but # of O varies

  • -ate has one more oxygen

  • -ite has one less oxygen


Compound names and formulas
Compound Names and Formulas tendency to attract the bonding pair of electrons, and so it will be found

  • Naming Ionic Compounds

    • Names of cations include the elements of which they are composed

    • Na+ is the sodium ion

    • Ca2+ is the calcium ion

  • Group 1 elements = +1

  • Group 2 elements = +2


  • Naming Anions tendency to attract the bonding pair of electrons, and so it will be found

  • Have altered element names

  • Replace ending with –ide

  • F- is Floride ion

  • O 2- is Oxide ion

  • Refer to chart 5 pg 160


Transition metal cations
Transition Metal Cations tendency to attract the bonding pair of electrons, and so it will be found

  • Refer to chart 6 pg 160


Determining the charge of a transition metal cation
Determining the charge of a transition metal cation tendency to attract the bonding pair of electrons, and so it will be found

  • All compounds have a total neutral charge of zero. (+ = -)

  • Fe2 O3

  • Know oxide ion is –2

    3 O would have a charge of –6 ( 3x –2)= -6

  • Charges must = 0 so +6 must be the + charge

    for 2 Fe to have a +6 charge, the Fe must have a 3+ charge


Naming covalent compounds
Naming Covalent Compounds tendency to attract the bonding pair of electrons, and so it will be found

  • Refer to table 7 page 162 know prefixes!

    • N2 04 is dinitrogen tetraoxide


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