Lap 7 Notes Handout Review and Section 7.1
Review using shell diagrams
Nobel gases all have 8 electrons in their outermost energy level, except for helium, which has a
full 1s orbital with 2 electrons, making them very _______________________ and unreactive.
(Noblemen of medieval times did not socialize with lower classes.) Also called _______________
A. Valence electrons
Def: ___________________________________________________________________
Determine _____________________ of elements
All elements in same _________________ on periodic table have the same # of valence
electrons. So have the same properties.
Valence electrons are the _______________________ electrons used in chemical bonding
B. Electron dot structures
Diagrams that show valence electrons as dots
Symbol of the element is used, surrounded by dots for the valence electrons
All electron dot diagrams are the ________________ for all elements in the same group
To draw an electron dot diagram: find the # of valence electrons for that element
Remember: this is the # of electrons in the outer energy level
(Put an electron dot structure on each group in shells notes)
Example: Lithium = _____ valence electron
Example: Boron = _____ valence electrons
Example: Nitrogen = _____ valence electrons
Example: Fluorine = _____ valence electrons
C. The Octet Rule (8)
When forming compounds, atoms tend to achieve
the electron configuration of a ______________________________- the nearest one
Try to get a full outer level of ________ electrons
Metals tend to lose electrons leaving a complete octet in next lowest energy level
Have less electrons in outer level, easier to lose
Result in forming a positive ion
Called _________________
Nonmetals tend to gain electrons to reach a full outer level
Have more electrons in outer level, easier to add
Result in forming a negative ion
Called _________________
Ionic bonds form because the ions have opposite charges - opposite charges
_______________, holding the ions together.
D. Formation of Cations
Losing electrons causes a positive charge
Names of metal cations are the ___________________ as the element name
Example: __________________________ = Na1+ or Na+
Sodium has lost 1 electron
Example: ___________________________ = Mg2+
Magnesium has lost 2 electrons
Example: Aluminum ion = Al3+
Aluminum has lost 3 electrons
Sodium ____________ has the same electron dot diagram as _______________
Na
1s22s22p63s1
Na+ 1s22s22p6
Loss of valence electron = ionization
ionization - the formation of or separation into ions by heat, electrical discharge, radiation, or
chemical reaction.
The sodium atoms in a sodium-vapor lamp ionize to form sodium cations.
Outside the arc of
electricity, ions recombine with electrons and light is emitted (photons) - yellow for sodium.
How do lithium, sodium, magnesium and aluminum lose electrons to look like the nearest noble
gas?
The electron configuration of Li, Li+, and He
Li 1s22s1
Li+ 1s2
He 1s2
The electron configuration of Na, Na+, and Ne
Na
1s22s22p63s1
Na+ 1s22s22p6
Ne
1s22s22p6
The electron configuration of Mg, Mg2+, and Ne
Mg
1s22s22p63s2
Mg2+ 1s22s22p6
Ne
1s22s22p6
The electron configuration of Al, Al3+, and Ne
Al
1s22s22p63s23p1
Al3+ 1s22s22p6
Ne 1s22s22p6
Cations of Group 1A elements always have a charge of _______ , indicated by +
Cations of Group 2A elements always have a charge of _______
Cations of Group 3A elements always have a charge of _______
Transition metals are an _______________________ to the Octet Rule
Ions formed _______ __________ have noble gas configurations
Iron, Fe, may lose two e-, Fe2+ or 3 e-, Fe3+
Silver, Ag has electron configuration of
1s22s22p63s23p63d104s24p64d105s1
would need to lose 11 e- to be like krypton
would need to gain 7 e- to look like xenon
_______________________ to lose or gain : ions with charges
of 3 or more are uncommon
Instead, it loses its 5s1 e- to be 4s24p64d10, with 18 e- in outer energy level
= ____________________ noble-gas electron configuration
(psuedo= not actually, resembling, mock)
Becomes Ag+
Other elements with psuedo noble-gas configurations:
gold Au+
cadmium Cd2+
mercury Hg2+
E. Formation of Anions
Gaining electrons causes a ______________________ charge
Names of anions are ________________ the same as the element
Anion names end in –ide
The element name ending is dropped and then –ide is added
Example: O2- is _____________________
Oxygen – ygen + ide
Oxygen has gained 2 eExample: Cl1- or Cl- is _________________
Chlorine – ine + ide
Chlorine has gained 1 eChloride ____________ has the same electron dot diagram as ________________
Cl
1s22s22p63s23p5
Cl- 1s22s22p63s23p6
How do fluorine, oxygen, nitrogen and sulfur gain electrons to look like the nearest noble gas?
The electron configuration of F, F-, and Ne
F 1s22s22p5
F- 1s22s22p6
Ne 1s22s22p6
The electron configuration of O, O2- and Ne
O
1s22s22p4
O2- 1s22s22p6
Ne
1s22s22p6
The electron configuration of N, N3-, and Ne
N
1s22s22p3
N3- 1s22s22p6
Ne
1s22s22p6
The electron configuration of S, S2- and Ar
S
1s22s22p63s23p4
S2-
1s22s22p63s23p6
Ar
1s22s22p63s23p6
When halogens (Group 7A) gain e-, they are called ________________ __________
They need only 1 e- to be a noble gas; very reactive
Common anions from the periodic table include:
Nitride and phosphide
Oxide and sulfide
need to gain ____ electrons so have a -3 charge.
need to gain _____ electrons so have a -2 charge.
Fluoride and chloride and bromide and iodide need to gain ____ electron so have a -1 charge.
Textbook pg 193 Sample problem
Write the symbol and name of the ion formed when
a.
An iodine atom gains one electron ______________________________
b. A strontium atom loses two electrons _____________________________
Write the symbol and name of the ion formed when
a. A sulfur atom gains two electrons ________________________________
b. An aluminum atom loses three electrons ____________________________
7.1 Section Assessment
1. How can you determine the number of valence e's in an atom of a representative element?
2. Atoms of which elements tend to gain electrons? Lose electrons?
3. How do cations form?
How do anions form?
4. How many valence electrons are in each atom?
potassium
carbon
magnesium
oxygen
5. Draw the electron dot structure for each element in Question 7.
6. How many electrons will each element gain or lose in forming an ion?
calcium
fluorine
aluminum
oxygen
7. How many electrons are lost or gained in forming each ion?
a. Ba2+
b. As3-
8. Write the name and symbol of the ion formed when
a potassium atom loses one e-
c. Cu2+
a zinc atom loses 2 ea fluorine atom gains 1 e-
9. Name each ion, identifying it as a cation or an anion.
a. Br-
b. Na+
c. Ca2+
d. O2-
10. Write the electron configuration of K+, Ca2+ and Ar and comment on the result.
K+
Ca2
Ar
7.2 Ionic Bonds and Ionic Compounds
Ionic compounds are often called salts, and are usually composed of a ______________ cation
(left side of periodic table) and a ________________ anion (right side of periodic table). They
do not form molecules, but instead form _______________________ ________ units of ions
with strong attraction for oppositely charged ions.
A. Formation of Ionic Compounds
usually formed from metal cations plus nonmetal anions
compounds formed are electrically __________________ :
total positive charge of cations _______ total negative charge of anions
opposite charges attract by means of ______________________ ________________
called ionic bonds
The sodium and chlorine atoms combine in a ______ ratio to form NaCl, and they both have
stable octets.
Aluminum and bromine react to form the compound aluminum bromide.
Al in group 3: has 3 valence e-'s to lose
Br in group 7: has 7 valence e-'s; wants one more
When they react, three bromine atoms combine with each aluminum atom,
forming aluminum ions and bromide ions.
They form aluminum bromide, AlBr3
The ratio of aluminum cations to bromide ions is 1:3, so the formula unit is AlBr3
chemical formula - shows the kinds and numbers of atoms in the smallest representative unit of
a substance
formula unit- the lowest _________________________________ of ions in an ionic compound
NaCl is the chemical formula for sodium chloride. But the formula NaCl does not represent a
single discrete unit. Because an ionic compound exists as a _____________________ of
positively and negatively charged ions arranged in repeating patterns, its chemical formula
refers to a ratio known as a _________________________________________.
Textbook pg 196
Use electron dot structures to predict the formulas of the ionic compounds formed from the
following elements:
Potassium and oxygen
cation named first, then anion
metal keeps name, nonmetal gets “ide”
Magnesium and nitrogen
cation named first, then anion
metal keeps name, nonmetal gets “ide”
Use electron dot structures to determine the formula of the ionic compound formed when
potassium reacts with iodine
Start with the atoms. To have a full octet, potassium needs to lose one e- and iodine needs to
gain one e-. Electrons lost need to equal electrons gained, so they will combine in a 1:1 ratio.
The formula for potassium iodide is _________
cation named first, then anion
metal keeps name, nonmetal gets “ide”
Use electron dot structures to determine the formula of the ionic compound formed when
aluminum reacts with oxygen
Start with the atoms. To have a full octet, aluminum needs to lose three e- and oxygen needs
to gain two e-. Electrons lost need to equal electrons gained (ionic compounds are neutral), so
they will combine in a 2:3 ratio.
aluminum oxide is _______________
cation named first, then anion
metal keeps name, nonmetal gets "ide"
Properties of Ionic Compounds
Most form crystals at room temp
Ions are arranged in repeating 3D patterns
ionic solids are _____________________ of ___________________________________.
not particles joined to form molecules
orderly arrangement produces beauty
Usually have very high melting and boiling points
Why? ions of opposite charges surround each other- strong attraction, very stable
coordination number of an ion is the number of ions of opposite charge that
surround the ion in a crystal
internal crystal structures are _______________________ for different compounds
Tend to be _______________ - if hit with a hammer, specific arrangement of ions is disturbed,
and repulsive charges can force crystal to fragment
Conduct ______________________________ when melted or dissolved in water
Do not conduct electricity when solid crystal lattice; ions fixed
When melted or dissolved, orderly crystal structure breaks down and ions are free
to move about; + ions move to negative electrode and - ions move to positive electrode
7.2 Section Assessment
1. How can you describe the electrical charge of an ionic compound?
2. What properties characterize ionic compounds?
3. Define an ionic bond.
4. Write the correct chemical formula for the compounds formed from each pair of ions.
a. K+, S2b. Ca2+, O2c. Na+, O2d. Al3+, N3-
6. Write formulas for each compound.
a. barium chloride
b. magnesium oxide
c. lithium oxide
d. calcium fluoride
7. Which pairs of elements are likely to form ionic compounds?
a. Cl, Br
b. Li, Cl
c. K, He
8. Identify the kinds of ions that form each ionic compound.
a. calcium fluoride, CaF2
b. aluminum bromide, AlBr3
c. lithium oxide, Li2O
d. aluminum sulfide, Al2S3
e. potassium nitride, K3N
9. Why does molten MgCl2 conduct a current but crystalline MgCl2 does not?
d. I, Na