Chemical Bonding Flashcards
Compound
is a substance that is made up of two or more different elements combined together chemically.
Octet Rule
that when bonding occurs, atoms tend to reach an electron arrangement with eight electrons in the outermost shell.
An Ion
is a charged atom or group of atoms.
An Ionic Bond
is the force of attraction between oppositely charged ions in a compound.
A transition metal
is one that forms at least one ion with a partially filled d sublevel.
Molecule
is a group of atoms joined together. It is the smallest particle of an element or compound that can exist independently
What is the smallest particle of an element or compound that can exist independently?
Molecule
What is the valency of an element defined as?
Valency of an element is defined as the number of atoms of hydrogen or any other monovalent element with which each atom of the element combines.
Electronegativity
is a measure of the relative attraction that an atom in a molecule has for the shared pair of electrons in a covalent bond.
What does a difference > 1.7 in electronegativity indicate?
difference > 1.7 indicates ionic bonding in a compound
What does a difference lower or equal to 1.7 in electronegativity indicate?
An electronegativity difference lower or equal to 1.7 indicates covalent bonding in a compound.
What happens to the value of electronegativity down the groups in the Periodic Table?
decrease down the groups in the Periodic Table for two reasons: increasing atomic radius and screening effect of inner electrons
What happens to the value of electronegativity across the periods in the Periodic Table?
The values of electronegativity increase across the periods in the Periodic Table for two reasons: increasing nuclear charge and decreasing atomic radius.
What is the most electronegative element?
F = most electronegative element (flourine)
What happens as you go down the group of halogens and why?
Halogens - decrease in reducing power down the group due to drop in electronegative values.
Compound
A compound is a substance that is made up of two or more different elements chemically combined. Element+Element=Compound
What are atoms held together by?
Chemical bonds
What is special about noble gases?
Noble gases have 8 electrons on their outer shell and are quite stable. Generally unreactive.
Are noble gases reactive?
Generally unreactive
What is helium used in and why?
Airships as it is lighter than air
How heavy is helium compared to hydrogen and why is it especially good to be used in airships?
Not as light as hydrogen [twice as heavy per volume] but does not burn
What does helium do to the voice and why?
It gives the diver a “Mickey Mouse” voice because it has such a low density compared to air
What is the most common Noble Gas?
argon
What is argon used for?
Used to fill normal light bulbs to stop them imploding
What happens when bonding occurs?
When bonding occurs, atoms tend to reach an electron arrangement with 8 electrons in the outer shell
What are the limitations of the octet rule?
Hydrogen, Lithium, Transition elements
What is valency?
Valency is the number of bonds an atom makes when it reacts.
How can the valency be worked out?
By calculating the number of electrons an atom needs to lose/gain to have 8e- on it’s outer shell.
How can valency be predicted?
From the periodic table
What does ammonia contain and what is it’s chemical formula?
Ammonia contains only Nitrogen and Hydrogen. It’s chemical formula is NH3.
What does methane contain? What is it’s chemical formula?
Methane contains only carbon and hydrogen. It’s chemical formula is CH4.
What is the chemical formula of Calcium Bromide?
CaBr2
What is the chemical formula of Silicon Flouride?
SiF4
What is a transition metal?
A transition metal is one that forms at least one ion with a partially filled d sublevel
What are features of transition elements?
Transition elements have variable valency, form coloured compounds and are used as catalysts.
What are exceptions to transition elements?
Exceptions: Zinc (Zn) and Scandium (Sc)
What is an ion?
a charged atom or group of atoms
What is involved in Ionic Bonding?
Electrons are transferred and ions are formed
are cations positive or negative?
positive
are anions positive or negative?
negative
What is an ionic bond?
the force of attraction between oppositely charged ions in a compound
What is ionic bonding usually between?
Ionic bonding usually between Groups 1 and 2 (Metals) and Groups VI and VII (Non-metals)
Draw dot and cross diagrams
.
What structure do ionic substances usually form and give an example.
Ionic substances usually form a structure called a crystal lattice e.g. NaCl
Why do ionic substances form crystals?
Ionic substances form crystals because positive ions attract negative ions in all directions
What are the characteristics of ionic substances?
Strong forces between the ions means it is very hard to break up the lattice structure.
Cannot conduct electricity when solid.
Most dissolve in water.
When dissolved the ions can conduct electricity
What is the result of ionic substances having strong forces between ions?
- High melting points and boiling points
- Usually solid at room temperature
Why are ionic substances not able to conduct electricity when solid?
- Ions not free to move and carry electricity
What are examples of everyday ionic substances?
Table Salt - Sodium Chloride (NaCl)
Flouridation in water to prevent tooth decay
- Sodium Fluoride (NaF)
What are the main complex ions with one negative change and their formulae?
Hydroxide ion (OH-), Nitrate ion (NO3-), Hydrogencarbonate ion (HCO3-), Permanganate ion (MnO4-)
What are the main complex ions with two negative charges and their formulae?
Carbonate ion (CO3 2-), Chromate ion (CrO4 2-), Dichromate ion (Cr2O7 2-), Sulfate ion (SO4 2-), Sulfite ion (SO3 2-), Thiosulfate ion (S2O3 2-)
What are the main complex ions with three negative charges and their formulae?
Phosphate ion (PO4 3-)
What are the main complex ions with one positive charge and their formulae?
Ammonium ion (NH3+)
Covalent bond
Formed when atoms share electrons
Give examples of covalent bonds
H2 - Hydrogen molecule
Cl2 - Chlorine molecule
What is a single bond and give an example
1 pair of electrons shared - H2
What is a double bond and give an example
2 pairs of electrons shared - O2
What is a triple bond and give an example
3 pairs of electrons shared - N2
Draw dot and cross diagrams for H2, O2 and N2
.
What are bonding pairs?
Shared electron pairs that form covalent bonds
What are lone pairs?
Electron pairs not involved in bonding
What happens to orbitals in a convalent bond?
they overlap
What is a sigma bond formed by?
Formed by the head-on overlap of two orbitals (can be s-orbitals or p-orbitals)
What is a pi-bond formed by?
Formed by the sideways overlap of p-orbitals
What type of bond is stronger and why?
Sigma bonds are stronger than pi bonds as there is more overlap between orbitals
How many sigma bonds and pi bonds in a double bond?
One sigma and one pi
How many sigma bonds and pi bonds in a triple bond?
One sigma and two pi
What are the features of ionic bonding?
Transfer of electrons, ions formed, high melting and boiling points, usually solid at room temp., conduct electricity when dissolved in water or molten (the ions are free to move in these stated)