Chapter 7
Two atoms held together by sharing one pair of electrons are joined by a ________________.
single covalent bond
Oxygen is in Group 6A, and an oxygen atom has _____ valence electrons.
six
Each ion is attracted strongly to each of its neighbors, and repulsions are minimized. The large attractive forces result in a very ___________________
stable structure
A ______________________- represents the covalent bonds as dashes and shows the arrangement of covalently bonded atoms.
structural formula
The __________ are not necessarily the lowest whole-number ratios.
subscripts
A molecular formula reflects ______________ of atoms in each molecule.
the actual number
Similarly, a bond formed by sharing three pairs of electrons is a ______________________.
triple covalent bond
An oxygen atom attains the electron configuration of neon by gaining _____ electrons.
two
____________________ also describe molecules consisting of atoms of one element.
Molecular formulas
Are molecules that do not obey the octet rule necessarily unstable?
No. There are molecules like NO2 that do not obey the octet rule, but that are stable, naturally occurring molecules.
Formation of Anions:
The gain of negatively charged electrons by a neutral atom produces an anion.
Group 1A Cations
When forming a compound, an atom loses its valence electron and is left with an octet in what is now its highest occupied energy level.
A covalent bond in which one atom contributes both bonding electrons is a _____________________.
coordinate covalent bond.
Atoms that are held together by sharing electrons are joined by a ______________
covalent bond
Combinations of atoms of the nonmetals and metalloids in Groups 4A, 5A, 6A, and 7A of the periodic table are likely to form _____________________.
covalent bonds
A variety of ______________ and ____________ can be used to show the arrangement of atoms in a molecule.
diagrams and molecular models
A ____________________ is a bond that involves two shared pairs of electrons.
double covalent bond
The electrostatic forces that hold ions together in ionic compounds are called ______________
ionic bonds
An ____________ is a compound composed of cations and anions.
ionic compound
Metallic atoms tend to ____________ valence electrons to produce a positively charged ions.
lose
Atoms of _____________- tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level.
metals
A compound composed of molecules is called a ___________________
molecular compound
Water is an example of a ___________________.
molecular compound
In contrast to ionic compounds, which are formed from a metal combined with a nonmetal, most __________________________ are composed of atoms of two or more nonmetals.
molecular compounds
The name of an anion of a nonmetallic element
-The name of the anion typically ends in -ide. -Thus, a chlorine atom (Cl) forms a chloride anion (Cl-). -An oxygen atom (O) forms an oxide anion (O2-)
Cations of Group 1A elements always have a charge of ____
1+
the loss of one unit of negative charge produces a cation with a charge of _________
1+
All halide ions (F-, Cl-, Br-, and I-) have a charge of ______
1-
Common Anions (Monoatomic and Polyatomic)
1- F- Fluoride, Cl- Chloride, Br- Bromide, I- Iodide OH- Hydroxide, ClO- Hypochlorite, NO3- Nitrate, C2H3O2- Acetate, HCO3- Hydrogen carbonate 2- O2- Oxide, S2- Sulfide, SO42- Sulfate, CO32- Carbonate 3- N3- Nitride, P3- Phosphide, PO43- Phosphate
Electron Configuration of Copper
Cu+ ion: 1s22s22p63s23p6 3d10 Cu2+ ion: 1s22s22p63s23p6 3d9
What property of nonmetallic elements makes them more likely to gain electrons than lose?
They have relatively full valence shells
______________ are the electrons in the highest occupied energy level of an element's atoms
Valence Electrons
Valence electrons are usually the only electrons involved in ___________________.
chemical bonds
Atoms of nonmetallic elements attain noble-gas electron configurations more _____________ by gaining electrons than by losing them because these atoms have relatively full valence shells.
easily
Although they are composed of ions, ionic compounds are _____________. The total positive charge of the cations equals the total negative charge of the anions.
electrically neutral
Some ions formed by transition metals do not have noble-gas electron configurations (ns2np6) and are therefore _______________ to the octet rule.
expections
A ____________ is the lowest whole-number ratio of ions in an ionic compound.
formula unit
Elements of halogen family _____________ one electron to become halide ions
gain
Many molecular compounds are _________ or __________ at room temperature.
gases or liquids
The ions produced when atoms of chlorine and other halogens gain electrons are called ___________
halide ions
An atom of iron may lose__________________________________
two valence electrons, forming the Fe2+ cation, or three electrons, forming the Fe3+ cation.
A pair of valence electrons that is not shared between atoms is called an ____________________, also known as a lone pair or a nonbinding pair.
unshared pair
The number of _________________ largely determines the chemical properties of an element.
valence electrons
To find the number of ______________________ in an atom of a representative element, simply look at its group number.
valence electrons
The arrangement of atoms within a molecule is called its _____________________
molecular structure
Anions and cations have ____________ and attract one another by means of ______________________.
opposite charges electrostatic forces.
What does not the molecular formula show?
A molecular formula does not tell you about a molecule's structure. In other words, it does not show either the arrangement of the various atoms in space or which atoms are covalently bonded to one another.
Formation of Cations:
An atom's loss of valence electrons produces a cation, or a positively charged ion.
What is an electron dot structure?
An electron dot structure is a diagram that shows the symbol of an element and its valence electrons as dots
___________________ are diagrams that show valence electrons in the atoms of an element as dots.
Electron Dot Structures
Electron Configuration of Iron
Fe2+ ion: 1s22s22p63s23p6 3d6 Fe3+ ion: 1s22s22p63s23p6 3d5
Monoatomic cations: Group 2A
Be2+, Mg2+, Ca2+, Sr2+, Ba2+, Ra2+
What is resonance?
Because earlier chemists imagined that the electron pairs rapidly flip back and forth, or resonate, between the different electron dot structures, they used double-headed arrows to indicate that two or more structures are in resonance.
What are valence electrons?
Electrons in the highest occupied energy level of an element's atom
The octet rule cannot be satisfied in molecules whose total number of valence electrons is an __________ number.
odd
All halogen atoms have seven valence electrons and need to gain only ________ electron to achieve the electron configuration of a noble gas.
one
When sodium and chlorine react to form a compound, the sodium atom transfers its ________________________ to the chlorine atom.
one valence electron
Hydrogen gas consists of diatomic molecules whose atoms share only one pair of electrons, forming a _________________
single covalent bond.
The charges of cations of the _____________ may vary.
transition metals
Monoatomic cations: Group 3A
Al3+
Polyatomic cation:
Ammonium ion NH4+
When is anion produced?
An anion is produced when an atom gains one or more valence electrons.
Octet Rule
An octet is a set of eight. Atoms of each of the noble gases (except helium) have eight electrons in their highest occupied energy levels and the general electron configuration of ns2np6. -In forming compounds, atoms tend to achieve the electron configuration of a noble gas.
How did nonmetals and metalliods form anions?
Atoms of nonmetals and metalloids form anions by gaining enough valence electrons to attain the electron configuration of the nearest noble gas.
The valence electrons largely determine the ______________________ of an element.
Chemical Properties
What happens in a covalent bond?
In covalent bonds, electron sharing usually occurs so that atoms attain the electron configurations of noble gases.
What is the octet rule?
In forming compounds, atoms tend to achieve electron configuration of a noble gas which has 8 electrons in its highest occupied energy level
Monoatomic cations: Group 1A
Li+, Na+, K+, Rb+, Cs+, Fr+
Group 2A Cations
Magnesium (atomic number 12) belongs to Group 2A of the periodic table, so magnesium atoms have two valence electrons.
What is the electron configuration called that has 18 electrons in the outer energy level and all of orbitals filled?
Pseudo noble-gas configuration
The group number of _____________ in the periodic table is related to the number of valence electron it has.
Representative Element
Examples of Transition metals
Vanadium (III) V3+ Vanadium (V) V5+ Chromium (II) Cr2+ Chromium (VI) Cr6+ Manganese (II) Mn2+ Manganese (VII) Mn7+ Iron (II) Fe2+ Iron (III) Fe3+ Copper (I) Cu+ Copper (II) Cu2+ Lead (II) Pb2+ Lead (IV) Pb4+ Silver Ag+ Zinc Zn2+
Atoms are arranged in _________________ ways in space to form molecules with different molecular structures.
different
Molecular compounds tend to have relatively __________ melting and boiling points than ionic compounds.
lower
A _____________________ is the chemical formula of a molecular compound which shows how many atoms of each element a substance contains.
molecular formula
A ________________________ is a neutral group of atoms joined together by covalent bonds.
molecule
Atoms of some _______________ tend to gain electrons or share electrons with another nonmetal atom or atoms to achieve a complete octet.
nonmetals
The chemical formula of an ionic compound refers to a ___________________
ratio known as a formula unit.
Most nonmetallic atoms achieve a complete octet by gaining or ________________ electrons
sharing
Ionic bonds form when the combining atoms give up or accept electrons. Another way that atoms can combine is by ___________________.
sharing electrons
Properties of Ionic Compounds
1. Most ionic compounds are crystalline solids at room temperature. 2. Ionic compounds generally have high melting points. 3. Ionic compounds can conduct an electric current when melted or dissolved in water.
A magnesium atom attains the electron configuration of a neon atom by losing both valence electrons and producing a magnesium cation with a charge of ________
2+
Cations of Group 2A elements always have a charge of ___
2+
What representative units define molecular compounds and ionic compounds?
The representative unit of a molecular compound is a molecule. For an ionic compound, the smallest representative unit is a formula unit.
