Chapter 3 Test Flashcards
Chemical Bond
The attraction between the atoms or ions of a substance
Stable Octet
Atoms having 8 valence electrons
How can atoms become stable?
It is possible for atoms to acquire a stable octet by the loss or gain of electrons. Atoms could achieve this by sharing electrons between them, that is, by chemically bonding to one another
Ionic Bonding
A type of chemical bonding resulting from the attraction between oppositely charged ions formed when metallic atoms transfer electrons to nonmetallic atoms
Physical Properties of Ionic Compounds
- Solids at room temperature
- Poor conductors of electricity when solid, but good conductors when molten
- Have high melting and boiling points which indicates strong bonding
- Crystalline, hard but brittle
- Are often soluble inwater
What happens when an ionic bond is formed?
When an ionic bond is formed by electron transfer between a metal and a non-metal,all of the electrons lost by the metal must be gained by the non-metal.
when ionic bonds are formed, enough electrons must be transferred so that each ion produced is isoelectronic with a NOBLE GAS
Covalent Bonding
When a pair of electrons is SHARED between 2 atoms
Ex. H• + •H → H••H
(single bond H—H)
- more bonds = more stable*
Diatomic Molecule
Molecules that consist of the same atoms
Ex. H2, N2, O2, F2, Cl2, Br2, I2, At2
HOFBrICI
Lewis Structure
A formula in which single lines are used to represent shared pairs of electrons and dots are used to represent valence electrons not involved in bonding
Ex. CI— CI
Physical Properties of Covalent Compounds
- Exist as gases, liquids and solids at room temperature
- Solid covalent compounds are usually soft
- Covalent compounds usually evaporate readily
- Have low melting and boiling points
- Not soluble in polar substances, such as water, but are soluble in nonpolar substances such as gasoline or oil
- Do not conduct electricity in either liquid or solid state
(since they don’t dissociate into ions → no electrolytes→no conduction)
Double Covalent Bond
When 2 pairs of electrons are shared between 2 atoms
EX.O = O
Triple Covalent Bond
When 3 pairs of electrons are shared between atoms
Polar Molecule
A molecule with a slightly negative and a slightly positive end
Polar Covalent Bond
A covalent bond in which there is an unequal sharing of electrons
Electronegativity
A quantitative measure of the electron-attracting ability of the atoms in a molecule
→ the higher the #,the higher the electronegativity
it parallels ionization energy
The greater the difference in electronegativity between the 2 atoms involved in a polar covalent bond, the more polar the bond will be
EX.
EN CI = 3.0 — EN H = 2.1 —————— △EN = 0.9
What are the 2 factors that determine whether or not a molecule will be polar or non-polar?
- The polarity of the bonds
2. The arrangement of the bonds in a molecule
Increasing Electronegativity Difference:
Pure Covalent value?
Polar Covalent value?
Ionic value?
Pure Covalent: 0 - 0.5
Polar Covalent: 0.5 - 1.7
Ionic: 1.7 - 3.3
Octet Rule
When atoms combine, bonds form so that each atom finishes with an octet of valence electrons
Steps for Lewis Dot Diagram on Covalent Compounds
- Determine the central atom (the atoms with the most single valence electrons)
- Draw Lewis Dot Diagram around the central atom
- Pair the single valence electrons between the atoms
- Redraw diagram neatly and ensure each atom in the formula follows the octet or duet rule
Nomenclature
Naming chemical compounds and writing chemical formulas
Free State
Atoms that are bonded to other atoms of the same element: Diatomic Elements
Free Element
Atoms that are not combined with other atoms
Polyatomic Ions / Oxyanions
An ion, which contains 2 or more atoms
- all ending in -ate*
Naming Chemical Compounds Containing Only 2 Elements:
a) POSITIVE MONATOMIC IONS
b) STOCK SYSTEM (MULTIALENCE)
a) if the ion has only 1 oxidation #, then the name of the ion is the same as the name of the element
Ex. Na+ → sodium ion
b)if the ion has more than 1 oxidation #, then the name of the ion is the same as the name of the element, however, a ROMAN NUMERAL in brackets is added right after
Ex. Cu2+ → copper (II)
Naming Chemical Compounds Containing Only 2 Elements:
BINARY COMPOUNDS CONTAINING HYDROGEN + ANOTHER ELEMENT
a)compounds of hydrogen and a NONMETAL Groups 16 and 17 are named by writing the word “hydrogen” followed by the name of the NONMETAL ending in “ide”
EX. HCI → hydrogen chloride
b)compounds of hydrogen and a METAL are named by writing the name of the METAL followed by “hydride”
EX. NaH → sodium hydride
Naming Covalent Compounds
The less electronegative element is written first followed by y the name of the second element ending in “ide”. In addition, each element is preceded by a prefix, which indicates the number of atoms of that atom
* mono- is not used on the first element name*
EX. As2S3 → diarsenic trisulfide
Rules for Naming Oxyanions
- If the ion contains 1 MORE OXYGEN atom than the common ion→ per___ate
- If the ion contains 1 LESS OXYGEN atom →___ite
- If the ion contains 2 LESS OXGEN atoms than the common ion → hypo___ite
Prefix thio: an oxygen from an oxyanion is replaced by a sulfur
thio___ate → root of common oxyanion ends in ate
thio___ite → root of common oxyanion ends in ite
EX. Na3SPO3 = sodium thiophosphate
Acid
- is a compound which has a sour taste
- turns litmus paper red
- contains at least 1 hydrogen atom that can be replaced by metals
What are the 2 groups of acids?
- Binary Acids:
H + any anion (non-metal) - Oxyacids:
H + oxyanion
Naming Binary Acids
Consists of hydrogen and a NONMETAL from Group 16 or 17. They are named by writing the word “hydrogen” followed by y the name of the NONMETAL ending in “ide”
→ this is for formulas with a (g)
EX. HCI (g) → hydrogen chloride
Solutions of these compounds dissolved in water (aq) are acids. They are named by using the prefix “hydro,” the name of the nonmetal ending in “ic” and followed by the word “acid”
→ this is for formulas with an (aq)
EX. HCI (aq)→ hydrochloric acid
Rules for Naming Oxyacids
- ___ate →___ic acid
- per___ ate → per___ic acid
- ___ite →___ous acid
- hypo___ite → hypo___ous acid
Hydrates
Compounds containing water of hydration
→when aqueous solutions of many of the soluble salts are evaporated, a precise # of water molecules may be retained as the ions form crystals
Rules for Naming Hydrates
Name the first part of the formula according to the rules learned in previous lessons followed by a “prefix-hydrate”
EX. MgSO4•7H2O
→ magnesium sulfate• heptahydrates
Bases
A substance which increases the # of hydroxide ions present in an aqueous solution
→ there will be a hydroxide ion present (OH)
Rules for Naming Bases
Write the name of the metal followed by “hydroxide”
EX. NaOH → sodium hydroxide
How can metals conduct electricity?
Free electrons conduct electricity
When a negative and a positive electrode are placed on a metal, the valence electrons move away from the negative electrocode and toward the positive one creating an electric current. Because metal atoms have a small core charge and a large radius, their valence electr ons can move freely and conduct electricity through this electrical current
How can metals conduct heat?
Free electrons conduct heat
Because valence electrons in metals move freely, they can conduct heat quickly from one end of a metal object to the other
If you heat one end of a metal, the neat gives nearby electrons energy, and the electrons move faster. The rapidly moving electrons move through the metal and collide with the slower/colder electrons farther away, allowing for the metal to conduct heat from one end to the other.
How can metals reflect light?
Free electrons reflect light
Light is an electromagnetic wave, and when it strikes a metal, it causes free electrons near the surtace to vibrate. This in turn causes the light to change direction, consistent with the laws of reflection
How can metals be dented or crushed?
Free electrons permit metals to be dented and crushed
Metals can be bent, hammered and stretched because of their small core charges and large radii. This lets metals to be struck without breaking as the atom cores slip into new positions, and the free electrons flow around them.
Explain why an ionic compound can conduct electricity but a molecular compound can’t
An ionic compound can conduct electricity because it is made up of and dissociates into ions
when it is in the form of an aqueous solution. And in this state, the ions are electrolytes so they can conduct electricity.
Molecular compounds can’t do this because they do not dissociate into ions, meaning there are no electrolytes to conduct electricity.
Describe dissolving at a molecular level
- the ions of an ionic compound dissociate in water
- Intermolecular attraction in H20 molecules becomes more distant
- H2O molecules hydrate the dissociated ions because of the attraction between the charges
