CHAPS Unit 6: Chemical Bonding

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