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6.1-6.13
What is chemical bonding?
mutual force of attraction between atom’s nucleus and electrons around it and strong attractive force that exists between atoms in a molecule
Why do chemical bonds form?
atoms involved in bonding process are seeking the lowest possible energy and most stable state
What is the lowest possible energy state?
ground state
When do atoms become more stable?
when they acquire electron configuration of a noble gas
What is the octet rule?
tendency of atoms to desire 8 electrons in valence shell
What happens to energy when a bond is formed?
released
What is true of the bond forming process?
exothermic
When is energy released in forming bonds?
electrons of valence shells settle into lower principle energy levels
What happens to energy when a bond is broken?
energy must be added
What is true of the bond breaking process?
endothermic
What does BARF stand for?
break bonds, absorb energy
release energy, form bonds
What bond exchanges electrons?
ionic bond
What bond shares electrons?
covalent bond
What bond has the immersion of electrons?
metallic bond
Which electrons are involved in chemical bonding?
Valence electrons
What do Lewis-Dot Diagrams show?
valence electrons and roles in bond formation
What is true of the valence shell of group 18 elements?
full
What are positive ions?
cations
What are negative ions?
anions
Do metals lose or gain electrons?
lose
What is an ionic bond?
one or more electrons are transferred from valence shell of one atom to valence
What two elements are involved in ionic bonding?
a metal and a nonmetal
Which element in ionic bonds donates electrons?
metal
What does it mean if an atom gives up an electron?
low ionization energy
What does it mean if an atom readily gains an electron?
high electron affinity
What is the atomic size of metals?
large
What is the atomic size of non-metals?
small
What is the ionization energy of non-metals?
high
What is the ionization energy of metals?
low
What is the electronegativity of metals?
low
What is the electronegativity of non-metals?
high
What is the true of the heats of formation of ionic substances?
negative
Why is the formation of an ionic compound so exothermic?
loss of electrons from atom is endothermic and gain is exothermic
gain energy > loss energy
What does the positive energy change in ionic bond forming assume?
ions do not interact with each other
What is unaccounted for in the energy of ionic bond forming?
electrostatic attraction between newly formed cation and anion
What is lattice energy?
energy required to completely separate one mole of solid ionic compound into gaseous ions
relationship between atomic size and lattice energy
indirect
What do large positive lattice energies indicate?
ions are strongly attracted to one another in ionic solids
What does the magnitude of lattice energies depend on?
ion charges, sizes, and arrangement in solid
What is Coulomb’s law?
Eel = (kQ1Q2)/d
relationship between charge magnitude and lattice energy?
direct
relationship between distance between atom centers and lattice energy?
indirect
What ion do group 1 elements form?
+1 cation
What ion do group 2 elements form?
+2 cation
What ion do group 13 elements form?
+3 cation
What ion do group 15 elements form?
-3 anion
What ion do group 16 elements form?
-2 anion
What ion do group 17 elements form?
-1 anion
What energy level do you remove electrons from?
highest energy level
Why do metals readily lose electrons?
low ionization energy
Why do nonmetals readily gain electrons?
high electronegativity and electron affinity
What is true of the BP of ionic compounds?
high
What is true of the MP of ionic compounds?
high
Why do ionic compounds have high MPs and BPs?
strong attractive force between positive and negative ions
What structure do most solids have?
crystal lattice
What is a crystal lattice?
definite repeating arrangement of elements
What happens to a solid when the crystal lattice structure is messed up?
cracks
What is needed for a substance to be conductive?
must contain moving charged particles
What is conductivity?
ability to conduct electric current
Are ionic solids conductive?
no
How can an ionic compound be conductive?
breakdown into individual ions in solution
When are ionic compounds conductive?
in (aq) or (l) form
Are ionic compounds malleable
yes
are ionic compounds hard?
yes
are ionic compounds brittle?
yes
why are ionic compounds brittle?
repulsion of same-charged particles
can ionic compounds be cleaved?
yes
are ionic compounds soluble?
yes
What is true of the electronegativity difference of ionic compounds?
>1.70
What is a covalent bond?
bond formed by 2+ atoms that share electrons
What happens to the valence orbitals in a covalent bond?
overlap each other
How are the electrons distributed in a covalent bond?
spend equal time in each valence orbital
What are the three electrostatic interactions in these bonds?
positive nuclei repel, negative electrons repel, electrons and nuclei attract
What does the covalent molecule being stable mean?
attractive forced overcome repulsive forces
How many electrons would group 17 elements form?
1
How many electrons would group 16 elements form?
2
How many electrons would group 15 elements form?
3
How many electrons would group 14 elements form?
4
What are molecular substances held together by?
covalent bonds
What is the valence bond theory?
bonding electron pairs are concentrated in region between atoms and nonbonding electron pairs lie in directed regions of space
Where does a buildup of electron density occur?
between two nuclei
When does a buildup of electron density occur?
valence orbitals overlap
What happens within the overlap of valence orbitals?
2 electrons of opposite spin share space between nuclei, forming covalent bond
orbital overlap and potential energy relationship?
indirect
bond length and potential energy relationship?
indirect
What happens when atoms are infinitely apart?
energy approaches 0
What happens when distance between atoms increase?
overlap between 1s orbitals increase, electron density between nuclei increase, PE decreases
relationship between bond strength and PE?
indirect
What happens as atoms come closer than .74 A?
energy increases sharply because nuclei repel
What is the bond length?
distance that corresponds to minimum of PE curve and at which attractive forces of unlike charges are balanced by repulsion between like charges
How many electron pairs are shared in single bonds?
1
How many electron pairs are shared in double bonds?
2
How many electron pairs are shared in triple bonds?
3
bond length and number of shared electron pairs relationship?
indirect because more attraction
What does the molecular formula show?
number and type of elements
What does the dot diagram show?
arrangement of valence electrons involved in bonding process
What does the structural formula show?
bonds and type, number, and arrangement of elements
What is always true of the central atom?
least electronegative
What is formal charge?
charge atom would have if all atoms in molecule had same electronegativity and each bonding pair was shared equally between two atoms
