3 chem bond incomplete*

Question 1

structure and bonding of an ionic compound

Answer 1

Ionic compounds in the solid state have a giant ionic lattice structure held together by *strong electrostatic forces of attraction** between oppositely charged ions in an ionic compound.

Question 1

what comes together to form ionic bonds and how to tell which is the anion and cation

Answer 1

Electrons are transferred from metal atoms to non-metal atoms to form ions that come together in a solid ionic compound.
● The atom that transferred the electron(s) gets positive charge(s) and becomes a cation.
● The atom that gained the electron(s) get negative charge(s) and becomes an anion.

hence metals become cations and non-metals become anions

Question 2

Sodium forms the oxide Na2O. Explain why the oxide of sodium has this formula.

Answer 2

Each Na atom has one valence electron. To attain noble gas electronic configuration, each Na atom loses its valence electron to form a Na+ cation.

Each O atom has six valence electrons. To attain noble gas electronic configuration, each O atom gains two electrons from two Na atoms to form an O2– anion.

In the resultant giant ionic lattice formed, the ratio of Na+ : O2– is 2:1 such that the lattice is electrically neutral overall. Therefore, the formula is Na2O.

Question 3

physical properties of ionic compounds

Answer 3

▪ High melting and boiling points
▪ Soluble in water
▪ Conducts electricity in molten and aqueous state
▪ Hard, rigid and brittle

Question 4

Why do ionic compounds have high melting and boiling points?

Answer 4

Ionic compounds have a giant ionic lattice. In melting, large amount of energy is supplied to overcome the strong electrostatic forces of attraction between the oppositely charged ions to break the giant ionic lattice to form free ions.

Question 5

how is the strength of ionic bonding determined by the charge of the ions, and their radii.

Answer 5

The higher the charge and the smaller the radii of the ions(ionic radii), the stronger the ionic bonding.

Question 6

Between NaCl and MgO, which compound would be expected to have the higher melting point? Explain.

Answer 6

▪ Both NaCl and MgO have a giant ionic lattice.
▪ However, Mg2+ and O2─ have higher charge and smaller ionic radius than Na+ and Cl- (higher charge means more electromagnetic attraction = closer to nucleus)
▪ Hence the strength of the ionic bonds in MgO is larger than that of NaCl.
▪ More energy is needed to overcome the stronger electrostatic forces of attraction between the oppositely charged ions in MgO.
▪ MgO will have a higher melting point.

Question 7

What happens when an ionic salt dissolves in water?

Answer 7

When an ionic salt dissolves, each ion on the crystal’s surface attracts the oppositely charged poles of the polar water(solvent) molecules and the ions become hydrated (or solvated if solvent is another polar solvent). This hydration process releases energy. The ionic crystal structure breaks down and the solid dissolves.

Question 8

Why is it that ionic compounds do not conduct electricity in the solid state but conducts in the molten and in aqueous solutions?

Answer 8

Ionic compounds do not conduct electricity in the solid state as the ions are fixed in positions and are not free to move. In molten and in aqueous solutions, the ions are mobile. The ions are **free to move and flow towards the oppositely charged electrodes and act as mobile charge carriers, carrying a current.

Question 9

Why are ionic solids Hard, rigid and yet brittle

Answer 9

In an ionic lattice, oppositely charged ions are held in fixed positions throughout the crystal lattice by strong ionic bonding. Moving the ions out of position requires large amounts of energy to break these bonds. Ionic lattices are therefore quite hard and rigid.
However, if enough pressure (e.g. by cutting or knocking) is applied, ions of like charge are brought next to each other. Repulsion between ions of like charges will cause the lattice to shatter apart. Ionic lattices are therefore said to be brittle.

Question 10

structure and bonding of a metallic compound

Answer 10

Metals in the solid state have a giant metallic lattice structure, held together by metallic bonding. Metallic bonding is the electrostatic force of attraction between a lattice of metal cations and the sea of delocalised electrons in the metallic lattice.

Question 11

what affects Strength of metallic bond s

Answer 11

Number of delocalised valence electrons in the structure.
–>The larger the number of valence electrons contributed per atom, the greater the number of delocalised electrons and the stronger the metallic bonding.

Charge and radius of the metal cation.
–>The higher the charge and the smaller the radius of the metal cation, the greater electrostatic force of attraction between the cations and the sea of delocalised electrons.

Question 12

Physical properties of metals

Answer 12

▪ High melting and boiling points
▪ Conducts electricity
▪ Good conductor of heat
▪ Malleable and ductile
▪ Shiny surface
▪ Hard

Question 13

y doe metals have a High melting and boiling points

Answer 13

_Most metals are solids with moderately high melting points and much higher boiling points. Metals have a giant metallic lattice structure which consists of a lattice of metal cations with a sea of delocalised electrons and the electrostatic forces of attraction between the cations and the delocalised electrons constitute the metallic bond. _
metallic bonding spam

Melting and boiling points of metals are relatively high because a large amount of energy is required to overcome the relatively strong electrostatic forces of attraction between the cations and delocalised
electrons.

Question 14

Why are metals good electrical conductors?

Answer 14

Metals are good electrical conductors because the delocalised electrons which act as mobile charge carriers are free to move about in the solid structure.
When a piece of metal is attached to a battery, electrons flow from the negative terminal into the metal and replace electrons flowing from the metal into the positive terminal.

Question 15

malleable meaning

Answer 15

can be beaten into a sheet

Question 16

ductile meaning

Answer 16

can be pulled into wires

Question 17

Reasons for malleability and ductility:

Answer 17

▪ In the giant metallic structure, the metal ions are held in an orderly array.
▪ When an external force (e.g. hammering) is applied to a piece of metal, the layers of metal ions in the solid structure slide past each other and end up in new positions.
▪ The overall shape changes (the metal deforms) but the metal does not break because the sea of delocalized electrons prevents repulsions among the cations as they move past one another.
▪ The metallic bond strength remains the same.( the metallic bonds are able to maintain their integrity, enabling the metal to undergo plastic deformation without fracturing. )
▪ Metallic bonding is termed non-directional bonding. (Because metallic bonds are not limited to specific orientations, metals can be easily deformed in any direction without weakening the overall structure.)

Question 18

what are alloys

Answer 18

Alloys are mixtures of metals involving incorporation of small quantities of other element(s) into the pure
metal.

Question 19

why are alloys hard

Answer 19

Alloying makes metals harder. This is because atoms of the added metal have a different size. This will disrupt the orderly arrangement of the main metal atoms that can no longer slide over each other easily when a force is applied.

Question 20

what are covalent bonds

Answer 20

Covalent bonding is the electrostatic forces of attraction between the positively charged nucleus of both the bonded atoms and their shared pair of electrons.

Question 21

Formation of Covalent Bonds

Answer 21

The covalent bond is formed by an overlap of valence atomic orbitals. The resultant electron cloud is called a molecular orbital.

Question 22

how are sigma bonds formed

Answer 22

Sigma bonds are formed by the ‘head-on’ overlap of two atomic orbitals.

Question 23

how many sigma bonds can tajke place between 2 atoms

Answer 23

There can only be one sigma bond between two atoms as there is no other way for another head-on overlap of the atoms’ orbitals to take place.

Question 24

why is the only s orbital that can bond be from h

Answer 24

only valence electrons can bond and only h has the s orbital as the valence atomic orbital

Question 25

p atomic orbital look like

Answer 25

dumbell

Question 26

what are pi ponds

Answer 26

π bonds are formed by the **‘side-on’ overlap** of two atomic orbitals.

Question 27

is a pi bond or a sigma bond stronger

Answer 27

Side-on overlap is **less efficient** than head-on overlap as the **overlap is poorer**; hence a **π bond is weaker** than a **σ bond** and is _more_ **easily broken.**

Question 28

what is the only element that has to draw a **circle** instead of a **dumbell** when chemically bonding

Answer 28

hydrogen, as it is the only element with an s orbital as a valence shell

Question 29

which bond must exist first so the other can sigma or pi

Answer 29

For a π bond to exist, a **σ bond must first be present.**

Question 30

how many pi bonds can be between 2 atoms

Answer 30

There may be one or two π bonds between two atoms depending on the number of atomic orbitals involved in the bonding. There can be a **maximum of only 2 π bonds between two atoms.** (cuz got 3 p orbis, x y z, and x go to sigma bond so got 2 left that can become pi)

Question 31

what is the bond order

Answer 31

The number of covalent bonds formed between 2 atoms is called the **bond order.** A bond order of 3 indicates a triple bond. Multiple bonds are stronger and shorter than single bonds.

Question 32

whats the max number of covalent bonds 2 atoms can have

Answer 32

Depending on the type and number of atomic orbitals involved, it is possible to have more than 1 covalent bond formed between 2 atoms. **the max is 4** as there can be atoms with 4 valence e

Question 33

names of 1 bond 2 bond and 3 bond

Answer 33

single bond, double bond and triple bond

Question 34

what is a bond pair

Answer 34

In a covalent compound, an electron pair that is **shared between the bonded atoms** is called a bond pair.

Question 35

what is lewis structure drawing method

Answer 35

use line to represent one pair of bond pairs (a coavlent bond) still draw the other non bonded electrons on the atom

Question 36

What is electronegativity

Answer 36

It’s how much a molecule wants the electrons in a covalent bond

Question 37

general physcial properties of simple molecular substances

Answer 37

low melting point and low boiling point cannot conduct electricity insoluble in water soluble in organic solvents

Question 38

Y do simple molecular substances have the term simple in front

Answer 38

"simple molecular substances" refers to substances made up of molecules containing only a few atoms bonded together its also to contrast to other names like " giant covalent structures"

Question 39

what is the bond length

Answer 39

The bond length of a covalent bond is the **distance** between the **nuclei** of the 2 bonded atoms when their atomic orbitals overlap to form molecular orbitals. The bond length is essentially the sum of the covalent radii of the two atoms involved in the bond

Question 40

whats bond energy

Answer 40

The **strength of a covalent bond** is measured by the bond energy of that covalent bond. The bond energy of a covalent bond is the average energy required to **break** a particular bond in one mole of gaseous substance.

Question 41

relationship between size, length and strength of bonding in molecules

Answer 41

The smaller the atom, the shorter and the stronger the bond, and the larger the bond energy.

Question 42

The bond energy of the C─C single bond is 350 kJ mol–1 while the bond energy of a C=C double bond is 610 kJ mol–1. Why is the bond energy of the double bond less than double that of the single bond?

Answer 42

- A C─C single bond is made up of a σ bond while a C=C double bond is made up of a σ and a π bond. - A π bond is weaker than a σ bond (due to lower degree of orbital overlap) and thus the energy of a C=C double bond is not twice that of a C─C single bond.

Question 43

what is bond polarity

Answer 43

When two atom have the **same electronegativity**, the bonding electrons are shared **equally** and the covalent formed between the two atoms is **non-polar** . When two atom have **different electronegativity**, there is **unequal** sharing of bonding electrons and the covalent formed between the two atoms is **polar** .

Question 44

What’s partial positive/negative charge

Answer 44

The **more eN atom** has the greater tendency to attract the bonding electrons to itself --> **partial negative charge** (labeled **δ–**) due the build up of electron density around it. The other less eN atom in the bond then acquires a **partial positive charge** (labeled **δ+**).

Question 45

how to calculate electronegativity

Answer 45

Electronegativity increases across a Period and decreases down a Group. - bottom left is Fr least electronegative, top right is F most

Question 47

whats a dipole moment

Answer 47

ONLY IN POLAR BONDS. +--> dipole moment arrow # arrow points from the less eN atom to the more eN atom. The **greater** the **difference** in electronegativity, the **greater** the bond polarity and the **greater** its dipole moment.

Question 48

is a polar bond or non-polar bond stronger

Answer 48

For a covalent bond of the same bond order and similar bond length, a polar bond is **stronger** than a non-polar bond.

Question 49

whats a non polar molecule

Answer 49

DOESNT MEAN theres NO polar **bonds**, its js that the polar bonds CANCEL out each other by going in **opposing directions** **no overall dipole / overall dipole moment is zero.**

Question 50

what are intramolecular forces

Answer 50

covalent, ionic and metallic bonds INSIDE THE MOLECULE

Question 51

what are intermolecular forces

Answer 51

OUTSIDE THE MOLECULESS, attactign them tgt The attraction that exist between molecules in simple molecular elements or compounds are collectively referred to as intermolecular forces. intermolecular forces are electrostatic forces of attraction which arise from the interactions of the net dipole of simple covalent molecules.

Question 52

what are the 3 intermolecular forces

Answer 52

(a) Dispersion forces (London forces or 3instantaneous dipole-induced dipole interaction) (b) Permanent dipole-permanent dipole interactions (c) Hydrogen bonds

Question 53

what are the 2 van der Waals’ forces

Answer 53

(a) Dispersion forces (London forces or instantaneous dipole-induced dipole interaction) (b) Permanent dipole-permanent dipole interactions

Question 54

what are rewquirements for hydrogen bonds

Answer 54

● One molecule must contain a **H atom** directly bonded to a highly electronegative atom (**nitrogen, oxygen or fluorine**). ● The other molecule must contain an atom with a lone pair of electron on the highly electronegative atom (**nitrogen, oxygen or fluorine**).

Question 55

how do hydrogen bonds work

Answer 55

N-H O-H F-H bonds r super polar so all the electron density is withdrawn from H and the H has a poorly shielded proton aka significant δ+ charge. it can experience a particularly strong attraction from a lone pair of electrons on an adjacent molecule,

Question 56

how to draw hydrogen bonds

Answer 56

- rmbr to put the δ+- charges - draw the lone pairs for the N O F - hydrogen bonding is labbleed with like the zebra crossing |||||||||||||||| that

Question 57

whats the strongest intermolecular force

Answer 57

hydrogen bonding

Question 58

Factors affecting the strength of hydrogen bonding

Answer 58

- Bond polarity, more polar = stronger - extensiveness, Extent means how many hydrogen bonds can form between molecules. eg. water can form 4 per molecule, 2 pairs of lone on its oxygen + 2 hydrogen

Question 59

Main factor affecting the strength of dispersion forces

Answer 59

- The number of electrons per molecule. The greater the number of electrons in the molecules or atoms, the greater the electron cloud size, the greater the polarizability of the electron clouds, hence the stronger the dispersion forces. - shape, bigger surface area allow for more points of contact (more polarisable), resulting in stronger dispersion forces.

Question 59

effects of hydrogen bonding

Answer 59

stronger hydrogen bonds = - Relatively high melting and boiling points - Water has a high surface tension, high surface tension. hbonds hold it tgt - Structure and density of ice, Each water molecule is thus surrounded by four water molecules in a roughly tetrahedral arrangement.

Question 59

what are dispersion forces

Answer 59

Non-polar molecules are attracted to one another by instantaneous dipole – induced dipole interactions, also known as dispersion forces. However, dispersion forces exist in all molecules and can contribute significantly to the total intermolecular forces between polar molecules which have a large non-polar group in their structure.

Question 59

whats an instantaneous dipole

Answer 59

when a non polar molecule has an uneven distribution in the elctron cloud. like in its zone te elctrons js float around right but sometimes they both float to one side, then the neighbouring molecule will get an induced dipole cuz its own electroin gets repelled, so an instantaneous dipole – induced dipole interactions, **weak and very short-lived**

Question 60

Factors affecting boiling points of **non-polar** molecules

Answer 60

The stronger the dispersion forces, the higher the boiling points. NOTEEEE: During melting or boiling, only the weak intermolecular forces are broken/overcome, the strong covalent bonds are not broken.

Question 60

y do SIMPLE COVALENT MOLECULES have low Melting and boiling points

Answer 60

This is because **less** energy is needed to overcome the **weaker** intermolecular attractions between the discrete molecules

Question 60

y are SIMPLE COVALENT MOLECULES unable to conduct electricity

Answer 60

it has no no mobile charge carriers.

Question 61

Compound + Boiling point/°C Methane(CH4):−161 Ethane(C2H6):−89 Propane(C3H8):−42 All three compounds have _________structure. As the number of carbon atom increases from CH4 to C3H8, number of __________________ increases. Hence the size of the electron cloud _____________. Strength of _____________ between the molecules increases which requires _______________ to **overcome**. Hence boiling point increases from CH4 to C3H6.

Answer 61

simple molecular electrons increases dispersion forces **more** energy

Question 62

attraction exists between noble gas atoms?

Answer 62

dispersion forces

Question 63

noble gas 1 2 3, the boiling points r increasing Explain the difference in boiling points between these noble gases.

Answer 63

As the **number of electrons per atom _increases_** from 1 to 2 to 3, the **size of the electron cloud** of the atoms **increases**. Hence **dispersion forces between the atoms** becomes stronger and requires **more energy** to overcome.

Question 64

ionic vs covalent

Answer 64

ionic: -ionic bonding -giant ionic lattice structure, -stronger electrostatic forces of attraction between the oppositely charged ? n ? ions covalent: -covalent bonding -simple molecular structure. -weaker dispersion forces between ? molecules.