Bonding Flashcards
When atoms of the _________ elements combine with other atoms to form compounds, the atoms tend to achieve __ electrons (an octet) in the outermost or valence shell.
Provide four examples.
When atoms of the first 20 elements combine with other atoms to form compounds, the atoms tend to achieve 8 electrons (an octet) in the outermost or valence shell.
Some examples include carbon, oxygen, sodium and chlorine.
Hydrogen and lithium tend to have ___ valence electrons (a d____) in compounds. This is called a noble gas _______ or noble gas _______.
Hydrogen and lithium tend to have 2 valence electrons (a duplet) in compounds. This is called a noble gas configuration or noble gas structure.
Hydrogen:
Hydrogen has only one electron, and it needs to gain or share one more electron to achieve a stable electron configuration with two electrons in its first shell, similar to helium.
Lithium:
Lithium has three electrons, with one in its outermost shell. It can achieve a stable electron configuration by losing that one electron, leaving it with the same electron configuration as helium (two electrons in the first shell).
Since noble gases, like helium, neon and argon are _______, the conclusion is that the octet and duplet structure are _______.
Since noble gases, like helium, neon and argon are unreactive, the conclusion is that the octet and duplet structure are stable.
The idea about stability is simplistic for octet and duplet structures because there are _______.
For example, there are elements from _______, whose atoms combine with others to then have __________________. Also, elements like beryllium and boron can form compounds where the atoms do not achieve ____________.
The idea about stability is simplistic for octet and duplet structures because there are exceptions.
For example, there are elements from period 3 and higher, whose atoms combine with others to then have more than 8 electrons in their valence shell. Also, elements like beryllium and boron can form compounds where the atoms do not achieve 8 outer electrons.
Students sometimes use the phrase “ a fully-filled outermost shell” to mean the octet structure. This is to be ________.
In Bohr’s Model of the atom the first shell takes a maximum of ___ electrons, the second shell ____ electrons, and the third shell ____electrons. Thus a “full-filled” third shell refers to ____electrons, not ___. However, an atom such as argon (2.8.8) is _____ due to its __________________________ shell and not a ______ shell.
Students sometimes use the phrase “ a fully-filled outermost shell” to mean the octet structure. This is to be avoided.
In Bohr’s Model of the atom the first shell takes a maximum of 2 electrons, the second shell 8 electrons, and the third shell 18 electrons. Thus a “full-filled” third shell refers to 18 electrons, not 8. However, an atom such as argon (2.8.8) is unreactive due to its octet structure of 8 electrons in the outermost shell and not a fully-filled shell.
Example: Phosphorus Pentachloride (PCl₅)
Phosphorus (P) has 5 valence electrons and forms bonds with 5 chlorine (Cl) atoms.
Each chlorine atom shares one electron with phosphorus.
This results in 5 single covalent bonds, giving phosphorus 10 valence electrons instead of 8.
Why is this possible?
Phosphorus is in Period 3, meaning it has empty 3d orbitals that can hold extra electrons.
Example: Sulfur Hexafluoride (SF₆)
Sulfur (S) has 6 valence electrons and forms bonds with 6 fluorine (F) atoms.
Each fluorine shares one electron with sulfur.
This results in 6 single covalent bonds, giving sulfur 12 valence electrons instead of 8.
Why is this possible?
Sulfur is in Period 3, meaning it has empty 3d orbitals to accommodate more electrons.
All bonds are ______________. They hold __________ together.
All (yes ALL) bonds are electrostatic forces of attraction. They hold particles (atoms, molecules or ions) together.
There are ___ types of strong bonds and ___ collective type of weak bonds. What are they?
There are 3 types of strong bonds and 1 collective type of weak bonds.
The 3 types of strong bonds are ionic bond, covalent bond and metallic bond.
The weak bond is intermolecular forces.–> this only happen between molecules in a covalent compound (only in simple covalent molecules)
Ionic Bonding
This type of bonding occurs between ______ and _________.
Ionic Bonding
This type of bonding occurs between metallic elements and non-metallic elements.
How does ionic bonding work?
Metal atoms (with 1, 2 or 3 valence electrons) tend to lose electrons to form positively-charged ions (cations).
Non metal atoms (with 5,6 or 7 valence electrons) tend to gain electrons to form negatively-charged ions (anions).
For e.g. sodium (metal) reacts with chlorine (non-metal) to form sodium chloride.
The oppositely-charged ions attract each other and are held together by an __________________.
electrostatic force of attraction.
A specific sodium atom transfers its electron to a specific chlorine atom and the resulting ionic bond is formed only between the two particles.
True or false.
False. An ionic bond is formed between any two oppositely-charged ions. In an ionic solid, each positively-charged ion is attracted to several negatively-charged ions and vice versa.
Also, the term ‘molecules’ should not be used when describing an ionic compound. An ion pair, such as Na + Cl-, is not a molecule.
A dot and cross diagram is used to represent the arrangement of __________ in a compound.
In the context of ionic bonding, it shows ________________ but it does not imply _________________.
A dot and cross diagram is used to represent the arrangement of electrons in a compound.
In the context of ionic bonding, it also shows the ratio of positive ions to negative ions. The diagram does not imply that an ionic bonding is formed only between the ions shown.
What are the two types a dot and cross diagram can be represented as for ionic bonding?
- The dot and cross diagram of sodium chloride showing all electrons
- It also common to show only the outer electrons in dot and cross diagrams. Inner shell electrons and the circles denoting electron shells are omitted.—> usually that is how we draw it
Each ion is also attracted to other oppositely charged ions ___________.
At the same time
A more complete picture of ionic bonding is described using the structure of an ionic solid, a diagram that shows a ____________________ structure, exemplified by sodium chloride, NaCl.
Describe the structure and the bonds.
Giant ionic lattice structure
The ions are arranged orderly in a lattice, with ionic bonds between any oppositely charged ions. Note that each Na+ ions is bonded to 6 Cl- ions and vice versa.
The strength of the ionic bond is directly dependent on the quantity of charges on the ion. Thus the ionic bond between Na + and Cl - is weaker than the ionic bond between Mg 2+ and O2-.
The ionic bonding between Mg 2+ and O2- is stronger than that between Na + and F-. Based on the above information, state which ionic compound, magnesium oxide or sodium fluoride would have a higher melting point.
Magnesium oxide.
The Ca 2+ ion is ________ than the O2- ion.
Smaller
Each pair of Ca 2+ and O 2- constitutes a molecule. True or false.
False.
Molecule only applied for covalent bonding, however Ca 2+ ad O2- is an ionic bond.
When thinking about how atoms combine with other atoms to form ions or molecules, it is useful to consider that each atom would achieve a noble gas structure of ____________ electrons in the outer shell.
2 or 8
What are the exceptions to bonding in order to be stable?
Boron trifluoride
The centre boron atom has only 6 electrons in the outer shell while the three fluoride has 8 electrons.
In xenon fluoride, the central atom has 12 electrons in the outer shell.
These are examples where the scientific model cannot explain the behaviour of nature and thus new models are needed. In this case, the molecular orbital model was later proposed to explain these exceptions.
In general, when a metal reacts with a non-metal an ionic compound is formed. However, there are exceptions.
For example, ______ is an _______ with a ____ melting point of ________. This suggests that it is not _______ but has a __________
There is other evidence to suggest that _______ is not an ionic compound:
_________________________
_______________________
Its _____ melting point is, therefore, due to the ease in __________________
In general, when a metal reacts with a non-metal an ionic compound is formed. However, there are exceptions.
For example, lead (IV) chloride is an oily liquid with a low melting point of -15 degrees celcius. This suggests that it is not ionic but has a simple molecular structure. I.e. it is made up of small molecules.
There is other evidence to suggest that lead (IV) chloride is not an ionic compound:
It does not conduct electricity when molten i.e. in the liquid state and
It does not dissolve in water.
Its low melting point is, therefore, due to the ease in breaking the weak intermolecular forces that hold the molecules together.
It is important to note that during melting (or boiling) of simple covalent or simple molecular substances, ______________ are _________. Covalent bonds are _____ bonds, and breaking covalent bonds requires __________________.
It is important to note that during melting (or boiling) of simple covalent or simple molecular substances, covalent bonds are not broken. Covalent bonds are strong bonds, and breaking covalent bonds requires a lot of heat or energy.
Given the melting point of these three compounds, are they ionic or covalent?
Sodium chloride:
801 degrees celcius melting point
Magnesium chloride
714 degrees celcius melting point
Aluminium chloride
192 degrees celcius melting point
sodium chloride —> ionic
Magnesium chloride —> ionic
Aluminium chloride —> covalent
Not all metal and non metal are ionic. True or false?
True. You can determine if a compound is an ionic bond by checking the melting point and boiling point. Ionic bonds results in higher melting point and boiling point.
When drawing the dot and cross of a diagram, how can you ensure that your dot and cross diagram is accurate?
By ensuring that the total valence electron for the compound is the same as the one you have drawn.
There are also some other tips mentioned by deepseek—> you can control F and check again
What is a covalent bond?
A covalent bond occurs when two atoms share electrons from their outermost shell. Usually, each atom contributes one electron, so one covalent bod constitutes two electrons.
What are covalent substances?
Covalent substances can be made up units of small molecules (each molecule may be made up of 2 to more than 50 atoms) or can be a single giant unit made up of billions of atoms.
Covalent bonding can occur between ________________________ or ________________.
Covalent bonding can occur between atoms of the same element (non-metals) or between atoms of different elements.
What is some example of covalent bonding that occur between atoms of the same element (non-metals)?
e.g Hydrogen (H2), chlorine (Cl2), oxygen (O2) and nitrogen (N2)
Molecules can have single covalent bonds (one pair of electrons) between atoms, as with hydrogen, H-H and chlorine, Cl-Cl. There may be double bonds like 2 oxygen atoms sharing 2 pairs of electrons between them (O=O). A nitrogen molecule has a triple bond between the 2 nitrogen atoms (N three lines N). The above are examples of simple molecules.
There are two pairs of electrons on each oxygen atom and one pair of electrons on each nitrogen atom not shared or not involved in bonding. These are called _________________.
Lone pairs of electrons.
There are structures which comprise a very ________ number of atoms joined by ________ bonds. An example is diamond, which is made up of ______ atoms.
Describe the structure of diamond.
There are structures which comprise a very large number of atoms joined by covalent bonds. An example is diamond, which is made up of carbon atoms.
A piece of diamond may be considered a giant molecule. Each carbon is bonded to four other carbon atoms. All of the covalent bonds are strong bonds. The diagram shows the giant covalent lattice structure of diamond. This explains why diamond has a very melting point and is a hard and rigid solid.
What are some examples of covalent bonding that occur between atoms of different elements?
e.g. 2 atoms (hydrogen chloride, HCl), 3 atoms (carbon dioxide CO2), more than 3 atoms (ammonia, NH3, methane, CH4 and glucose, C6H12O6), and thousands of atoms (silicon dioxide, SiO2, also an example of a giant molecule).
In molecules such as carbon dioxide and ammonia, there is ____________.
One central atom.
The central atom is the element with the _________________________.
The central atom is the element with the least number of atoms in the molecule.
Are there molecules with more than one ‘central’ atom? Provide an example if so.
Yes. In the example below, ethane has 2 carbon atoms and 4 hydrogen atoms. The carbon atoms are regarded as central atoms. This reasoning can facilitate arranging atoms and electrons when drawing dot-and-cross diagrams.
Thus, covalent substances can have __________ or _____________.
Thus, covalent substances can have simple molecular structure or giant covalent structure.
Substances with simple molecular structure such as ____ and ______, are made up of __________ and are usually ________ or _______, or ______ with _______ melting points. The molecules are held together by _______________.
Substances with simple molecular structure such as O2, and CO2, are made up of simple molecules, and are usually gases or liquids, or solids with low melting points. The molecules are held together by weak intermolecular forces.
Substances with giant covalent structure, such as _______ and ________, have all their atoms ________ held together by _______________, thus they are _______ with _____ melting points.
Substances with giant covalent structure, such as diamond (C) and SiO2, have all their atoms strongly held together by covalent bonds in a large network, thus they are solid with high melting points.
Covalent bonding is often described as the sharing of electrons between atoms, and the atoms thereby ____________. Covalent bonding involves _______________________.
Covalent bonding is often described as the sharing of electrons between atoms, and the atoms thereby achieve a noble gas structure. Covalent bonding involves electrostatic forces of attraction.
What is the difference between simple molecules and a giant molecule?
The difference between these two groups of covalent substances is the presence of weak intermolecular forces. These weak forces are present in covalent substances with simple molecular structure. A low amount of heat would readily break the weak intermolecular forces. Hence, simple molecular substances like ammonia and carbon dioxide have low melting and boiling points.
During melting and boiling, the molecules remain intact. The strong covalent bonds between the atoms in each molecule are not broken.
By contrast, for covalent substances that have giant molecular structure, all the atoms are covalently and strongly bonded to each other. Melting would therefore involve breaking many covalent bonds between the atoms in the giant molecule. This requires a lot of heat. Hence, giant covalent substances like diamond and silicon dioxide have very high melting points.
What happens when ice melts and then water is boiled?
Example:
When ice melts and then water is boiled, only the intermolecular forces between the water molecules are broken. No covalent bonds are broken. No atoms of hydrogen or oxygen are produced.
What is the reason for metals to conduct heat and electricity.
Scientists believe that the valence electrons in each metal atom are shared equally by all the metal atoms, rather than being associated with a particular atom. These “free” electrons are the reason for the conductivity of heat and electricity by metals.
In sodium, each atom’s valence electron can ________ from the sodium atom, making the atom a __________. The ___________ can move freely ______ the metal and is described as a _____________. Hence, the structure of sodium may be viewed as ___________________________________________________. Hence, metallic bonding is the ________________________________________________,
In sodium, each atom’s valence electron can break free from the sodium atom, making the atom a positively charged ion. The valence electron can move freely throughout the entire metal and is described as a “delicacies” electron. hence, the structure of sodium may be viewed as an array of sodium cations embedded in a ‘sea’ or ‘cloud’ of freely moving delocalised electrons.
Hence, metallic bonding is the result of the electrostatic forces of attraction between positively-charged metal ions and negatively-charged delocalised electrons.
12 positive ions of sodium, Na +, each having a ____ charge, and _____ delocalised electrons are drawn.
Each having a 1+ charge and 12 delocalised electrons are drawn.
When presenting metallic bonding as a diagram, if x number of metal ions of y+ charge each is drawn, then the number of delocalised electrons must be ________________ because of _______________. The overall charge ______________.
the number of delocalised electrons must be xy because of conservation of change. The overall charge of a metal is zero, i.e. metals are neutral.
What are the properties of metal and why?
Metals can be beaten into sheets (malleable) and twirled or drawn into wires (ductile) because their atoms are arranged in layers, which can slide over each other easily.
Explain why metals have high melting points.
Metals generally have high melting points because the metallic bonds are strong. The metallic bonds are the electrostatic forces of attraction between the positive metal ions and the delocalised electrons.
Explain why metals can conduct electricity.
Metals conduct electricity because the delocalised electrons are able to move freely throughout the metal.
Explain why metals are malleable.
Metals are malleable (can be beaten into sheets) and are ductile (can be drawn as wires) because the layers of atoms in the metal lattice structure can easily slide over each other.
TAKE NOTE that it is layers of atoms and not layers of ions or layers of molecules.
Ionic and covalent bonding are two _______ models off the chemical bond. Most actual bonds lie somewhere __________________.
Ionic and covalent bonding are two extreme models of the chemical bond. Most actual bonds lie somewhere between purely ionic and purely covalent.
What is electronegativity?
Electronegativity is a measure of the the tendency of an atom to attract a bonding pair of electrons.
What are the four type of structures?
The four types of structures are: giant ionic, simple molecular, giant metallic and giant covalent.
What are allotropes?
Allotropes are different forms of the same element, where the atoms are arranged and bonded differently
What are two important allotropes of carbon?
Diamond and Graphite
The carbon atoms are packed in what structure?
The carbon atoms are packed in giant covalent structure, though arranged differently.
Does giant covalent structure have intermolecular forces of attraction?
Giant covalent —> one whole molecule—> atoms connected by covalent bond—> strong bonds—> don’t talk about intermolecular forces of attraction (IMF)
E.g. of giant covalent (silicon dioxide)
Describe the structure of a diamond?
The diamond solid structure has many strong covalent bonds between the carbon atoms. Every carbon atom is bonded to four other carbon atoms.
The arrangement of the 5 carbon atoms are in a tetrahedral geometry/structure.
As diamond has a giant covalent structure with all the atoms strongly bonded together, it is a very hard substance, being used to cut other hard solids.
Not a conductor of electricity, no free electrons to migrate.
Describe the structure of graphite?
Within each graphite layer each carbon atom is bonded to three other carbon atoms. This means the 4th valence electron of each carbon atom can be delocalised.
- between layers the forces are weak
- the layers can therefore easily slide over one another —> soft, slippery surface
These delocalised electrons are free to move within the layer and when a potential difference is applied across the layer these delocalised electrons then move in the same direction creating an electric current —> can conduct electricity.
In graphite solid, the carbon atoms are arranged in parallel layers. The layers can easily slide past each other when an external force is applied. This is because the forces holding the layers together are weak. Thus graphite is soft and slippery to touch.
What is the melting point of diamond and graphite?
3700 degrees celcius for diamond
3300 degrees celcius for graphite
What is the density for diamond and graphite?
3.5 g/cm cube for diamond
2.2 g/cm cube for graphite
What are the appearances of diamond and graphite?
Colourless, transparent crystals —> diamond
Black, shiny powder —> Graphite
Describe the property of hardness for diamond and graphite.
Diamond
- hardest natural substances known; used as drill tips for drilling equipment and in glass cutters.
- strong covalent bonds between carbon atoms are
- giant covalent structures of diamond
- the shape is a tetrahedron
Graphite
- soft. Used as a solid lubricant to reduce friction in engines, and also used as pencil lead.
- strong covalent bonds between carbon atoms
- weak forces of attraction between layers
- giant covalent structures of graphite
What is the reason for the difference in the hardness for diamond and graphite?
Diamond consists of many carbon atoms held together by strong covalent bonds. Each carbon atom is bonded to four other carbon atoms in the shape of a tetrahedron. The many covalent bonds make the structure rigid and strong. Thus, diamond is a very hard solid.
By contrast, each carbon atom in graphite is bonded to three other carbon atoms, forming a layer of hexagonal rings. Graphite is made of parallel layers of carbon atoms. Although strong covalent bonds hold the atoms together within each layer, between the layers are weak forces of attraction NOT IMF. This allow the layers to easily slide against each other when a force is applied. This makes graphite a soft solid.
For the property of electrical conductivity, what is it for diamond and graphite? What is the reason for this difference?
Diamond does not conduct electricity.
graphite conducts electricity.
Reason for difference:
In graphite, each carbon atom is covalently bonded to three other carbon atoms. This leaves each carbon with one valence electron not involved in bonding. This electron becomes delocalised and can move freely along the layer of carbon atoms, thus conducting electricity.
In diamond, each of the carbon atom’s four valence electrons is involved in covalent bonding with other carbon atoms, thus there are no delocalised electrons to move through the structure to conduct electricity.
What is the difference between solid sodium chloride and liquid sodium chloride? Why?
Solid sodium chloride does not conduct electricity, while liquid sodium chloride conducts electricity.
Reason:
The ions are held in fixed positions in the solid state and are not mobile. Thud solid ionic substances cannot conduct electricity. In the molten or aqueous states, the ions are mobile, acting as freely moving charge carriers to conduct electricity.
The melting point of sodium chloride is likely to be about
(A) 110 degrees celcius
(B) 801 degrees celcius
Why?
The melting point of sodium chloride is 801 degrees celcius, option B.
High m.p./b.p.
Reason:
Strong ionic bonds exist between the ions of opposite charges. A lot of heat is required to overcome these forces. —> Therefore, 801 degrees celcius
Describe the property of solubility in solvents for giant ionic structures.
Most ionic compounds dissolve in water, but do not dissolve in non-polar solvents.
Reason:
Water molecules are polar molecules and are thus attracted to ions in ionic compounds, since opposite charges attract. Water molecules thus surround the ions and pull them out of their lattice.
Non-polar organic solvents do not interact with ions.
Describe the property of melting/boiling points for simple molecular structures.
Low m.p./b.p.
Weak intermolecular forces are present between t eh molecules. It is these weak forces that are broken during melting and boiling.
Thus, only low heat is required to overcome these forces.
Note: The strong covalent bonds between the atoms in each molecules are not readily broken by heat. The molecule remains intact (no atoms are formed) when the substance changes state.
Describe the property of electrical conductivity for simple molecular structures.
Do not conduct electricity in any state
Reason:
The particles that make up the substance are neutral molecules. There are no charge carriers like mobile ions or delocalised electrons to conduct electricity.
Note:
Polar covalent molecules like HCl, HNO3, and H2SO4 dissolve EIP water to form acidic solutions containing free and mobile ions. The solutions of the acids can conduct electricity.
Describe the property of solubility in solvents for simple molecular structures.
In general, covalent substances do not dissolve in water and instead dissolve in organic non-polar solvents, like hexane.
Exceptions:
Small polar molecules, such as HCl and NH3, are soluble in water.
In comparing molecular substances, those that are made of more polar molecules are more soluble in water, because of the greater attraction between the substance’s molecules and water molecules.
Describe the property of melting/boiling points for giant metallic structures.
Generally high m.p./b.p.
Reason:
Strong metallic bonds exist between the positive metal ions and ‘sea’ of delocalised electrons.
A lot of heat is required to overcome these forces.
Note: The Group 1 metals (such as sodium) and mercury have low m.p and b.p. Compared to other metals.
Describe the property of electrical conductivity for giant metallic structures.
All metals conduct electricity in the solid and liquid states.
Reason:
A metal in the solid state comprises metal ions surrounded by a ‘sea’ of delocalised electrons. These electrons are mobile and can act as freely moving charge carriers to conduct electricity.
Describe the property of solubility in solvents for giant metallic structures.
Not soluble in any type of solvent.
Note: there are metals, such as sodium, that can react rapidly with water. So the metal will be observed to ‘dissolve’ as it reacts with water. This is NOT a physical dissolving but a chemical reaction.
Describe the property of melting/boiling points for giant covalent structures.
High m.p./ b.p.
Reason:
The particles are atoms which are held together by strong covalent bonds. The atoms are bonded to form an extensive network.
A lot of heat is required to break the many strong bonds.
Describe the property of electrical conductivity for giant covalent structures.
Do not conduct electricity in any state.
Reason:
The giant molecule is made up of atoms that are covalently bonded to each other. There are no charged particles i.e. free ions or delocalised electrons to act as charge carriers.
Exception:
Graphite is a non-metal that is a good conductor of electricity.
Reason:
Each carbon atom is bonded to three other carbon atoms forming layers. Each atom has a fourth valence electrons which is delocalised within each layer. These electrons are freely-moving, they can act as charge carriers to conduct electricity.
Describe the property of solubility in solvents for giant covalent structures.
Not soluble in any type of solvent.
Note:
The structures of silicon dioxide (or sand) and diamond comprises many strong covalent bonds between the atoms which require a lot of heat to break to separate the atoms.
